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D-/L-Lactic Acid (D-/L-Lactate) (Rapid) Assay Kit

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D- L-Lactic Acid D- L-Lactate Rapid Assay Kit K-DLATE Scheme
Product code: K-DLATE

100 assays (50 of each) per kit

Prices exclude VAT

Available for shipping

Content: 100 assays (50 of each) per kit
Shipping Temperature: Ambient
Storage Temperature: Short term stability: 2-8oC,
Long term stability: See individual component labels
Stability: > 2 years under recommended storage conditions
Analyte: D-Lactic Acid, L-Lactic Acid
Assay Format: Spectrophotometer
Detection Method: Absorbance
Wavelength (nm): 340
Signal Response: Increase
Linear Range: 0.5 to 30 µg of D- or L-lactic acid per assay
Limit of Detection: 0.21 mg/L
Reaction Time (min): ~ 10 min (L-lactic acid),
~ 5 min (D-lactic acid)
Application examples: Wine, soft drinks, milk, dairy products, foods containing milk (e.g. dietetic foods, bakery products, baby food, chocolate, sweets and ice-cream), vinegar, fruit and vegetables, processed fruit and vegetables, meat products, food additives, paper (and cardboard), cosmetics, pharmaceuticals and other materials (e.g. biological cultures, samples, etc.).
Method recognition: Methods based on this principle have been accepted by DIN, GOST, IDF, EEC, EN, ISO, OIV, IFU, AIJN and MEBAK

The D-/L-Lactic Acid (D-/L-Lactate) (Rapid) test kit is used for the rapid and specific concurrent measurement and analysis of L-lactic acid (L-lactate) and D-lactic acid (D-lactate) in beverages, meat, dairy and food products.

Note for Content: The number of manual tests per kit can be doubled if all volumes are halved.  This can be readily accommodated using the MegaQuantTM  Wave Spectrophotometer (D-MQWAVE).

Explore more organic acid assay kit products.

Scheme-K-DLATE DLATE Megazyme

  • Extended cofactors stability. Dissolved cofactors stable for > 1 year at 4oC.
  • Rapid total analysis time (concurrent / flexible D and L-lactic acid reaction format) 
  • D-lactate dehydrogenase reaction very rapid with most samples (~ 5 min) 
  • Very competitive price (cost per test) 
  • All reagents stable for > 2 years after preparation 
  • Mega-Calc™ software tool is available from our website for hassle-free raw data processing 
  • Standard included 
Megazyme publication

Megazyme “advanced” wine test kits general characteristics and validation.

Charnock, S. J., McCleary, B. V., Daverede, C. & Gallant, P. (2006). Reveue des Oenologues, 120, 1-5.

Many of the enzymatic test kits are official methods of prestigious organisations such as the Association of Official Analytical Chemicals (AOAC) and the American Association of Cereal Chemists (AACC) in response to the interest from oenologists. Megazyme decided to use its long history of enzymatic bio-analysis to make a significant contribution to the wine industry, by the development of a range of advanced enzymatic test kits. This task has now been successfully completed through the strategic and comprehensive process of identifying limitations of existing enzymatic bio-analysis test kits where they occurred, and then using advanced techniques, such as molecular biology (photo 1), to rapidly overcome them. Novel test kits have also been developed for analytes of emerging interest to the oenologist, such as yeast available nitrogen (YAN; see pages 2-3 of issue 117 article), or where previously enzymes were simply either not available, or were too expensive to employ, such as for D-mannitol analysis.

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Megazyme publication

Grape and wine analysis: Oenologists to exploit advanced test kits.

Charnock, S. C. & McCleary, B. V. (2005). Revue des Enology, 117, 1-5.

It is without doubt that testing plays a pivotal role throughout the whole of the vinification process. To produce the best possible quality wine and to minimise process problems such as “stuck” fermentation or troublesome infections, it is now recognised that if possible testing should begin prior to harvesting of the grapes and continue through to bottling. Traditional methods of wine analysis are often expensive, time consuming, require either elaborate equipment or specialist expertise and frequently lack accuracy. However, enzymatic bio-analysis enables the accurate measurement of the vast majority of analytes of interest to the wine maker, using just one piece of apparatus, the spectrophotometer (see previous issue No. 116 for a detailed technical review). Grape juice and wine are amenable to enzymatic testing as being liquids they are homogenous, easy to manipulate, and can generally be analysed without any sample preparation.

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Lentilactobacillus kribbianus sp. nov., isolated from the small intestine of a mini pig.

Bai, L., Paek, J., Shin, Y., Park, H. Y. & Chang, Y. H. (2020). International Journal of Systematic and Evolutionary Microbiology, 70(12), 6476-6481.

A Gram-stain-positive, facultative anaerobic, rod-shaped bacteria isolated from the small intestine of a mini pig was designated as strain YH-lac9T. 16S rRNA gene sequence analysis revealed that the strain belongs to the genus Lentilactobacillusand is closely related to Lentilactobacillus seniorisJCM 17472T, Lentilactobacillus rapiJCM 15042T and Lentilactobacillus diolivoransJCM 13927T, with 97.6, 96.2 and 95.7 % sequence similarity, respectively. Analysis of housekeeping gene sequences (pheS and recA) revealed that the strain formed a sub-cluster with L. senioris, supporting the results of 16S rRNA gene sequences analysis. The average nucleotide identity value for YH-lac9T and the most closely related strain is 74.1 %. The main fatty acids are C18 : 1ω9c, summed feature 7, C16 : 0 and summed feature 8. The G+C content of the genomic DNA is 37.8 mol%. In view of its chemotaxonomic, phenotypic and phylogenetic properties, YH-lac9T (=KCTC 25005=JCM 33997) represents a novel taxon. The name Lentilactobacillus kribbianus sp. nov. is proposed.

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Uncovering a superfamily of nickel-dependent hydroxyacid racemases and epimerases.

Desguin, B., Urdiain-Arraiza, J., Da Costa, M., Fellner, M., Hu, J., Hausinger, R. P., Desmet, T., Hols, P. & Soumillion, P. (2020). Scientific Reports, 10(1), 1-11.

Isomerization reactions are fundamental in biology. Lactate racemase, which isomerizes L- and D-lactate, is composed of the LarA protein and a nickel-containing cofactor, the nickel-pincer nucleotide (NPN). In this study, we show that LarA is part of a superfamily containing many different enzymes. We overexpressed and purified 13 lactate racemase homologs, incorporated the NPN cofactor, and assayed the isomerization of different substrates guided by gene context analysis. We discovered two malate racemases, one phenyllactate racemase, one α-hydroxyglutarate racemase, two D-gluconate 2-epimerases, and one short-chain aliphatic α-hydroxyacid racemase among the tested enzymes. We solved the structure of a malate racemase apoprotein and used it, along with the previously described structures of lactate racemase holoprotein and D-gluconate epimerase apoprotein, to identify key residues involved in substrate binding. This study demonstrates that the NPN cofactor is used by a diverse superfamily of α-hydroxyacid racemases and epimerases, widely expanding the scope of NPN-dependent enzymes.

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Thermophilic lactic acid bacteria affect the characteristics of sourdough and whole-grain wheat bread.

Cizeikiene, D., Jagelaviciute, J., Stankevicius, M. & Maruska, A. (2020). Food Bioscience, 38, 100791.

Application of selected starter cultures for sourdough propagation may ensure stable lactic acid bacteria (LAB) diversity and defined properties of sourdough that affect quality. The impact of Lactobacillus delbrueckii ssp. Bulgaricus MI, L. rossiae GL14 and L. acidophilus DSM 20079 as starter cultures were investigated for spoilage prevention and whole-grain wheat and sourdough bread properties. Whole-grain wheat sourdough propagated with these strains showed high phytase, amylase and xylanases activities. The highest phytase activity was obtained in sourdough prepared with L. bulgaricus MI. The results of gas chromatography–mass spectrometry using solid-phase microextraction showed that the compositions of volatile compounds in sourdough and whole-grain wheat bread depended on the LAB starter. In bread with L. acidophilus, 3-octen-2-ol and n-hexadecane were found, whereas those compounds were not found in other bread samples or in sourdough. Tetrahydrofurfuryl acetate was found only in bread prepared with L. bulgaricus MI sourdough. N-Pentadecane was found only in bread prepared with L. rossiae sourdough and bread prepared with spontaneous sourdough. The application of thermophilic sourdough increased bread porosity, elasticity, crumbliness and moisture content, but did not influence crumb hardness. Moreover, the fungal spoilage on the bread crust surface was suppressed using sourdough prepared with thermophilic LAB. The strain of LAB used for sourdough preparation influenced the shelf-life of bread.

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Improvement of Polymer Grade L-Lactic Acid Production Using Lactobacillus rhamnosus SCJ9 from Low-Grade Cassava Chips by Simultaneous Saccharification and Fermentation.

Unban, K., Puangkhankham, N., Kanpiengjai, A., Govindarajan, R. K., Kalaimurugan, D. & Khanongnuch, C. (2020). Processes, 8(9), 1143.

The present study aims to examine the process for L-lactic acid production from low-grade cassava chips (LGC) using a two-step fermentation approach (TSF) and simultaneous saccharification and fermentation (SSF) by proficient, newly isolated Lactobacillus rhamnosus strain SCJ9. The optimized medium composition revealed by response surface methodology for TSF was 166 g/L LGC hydrolysate and 20 g/L yeast extract (YE), while other medium components were fixed (g/L) as follows: tween80 (2.0), (NH4)2HPO4 (2.0), CH3COONa∙3H2O (6.0), (NH4)2HC6H5O7 (2.0), MgSO4∙7H2O (0.5), and MnSO4∙H2O (0.3). Based on the optimization conditions, the maximum experimental L-lactic acid of 134.6 g/L was achieved at 60 h fermentation time with a production efficiency of 89.73%, 0.95 g/g yield and 2.24 g/L/h productivity. In contrast, L-lactic acid production by SSF under optimized concentrations of thermostable-α-amylase (AA) and glucoamylase (GA) gave maximum L-lactic acid of 125.79 g/L at only 36 h fermentation time which calculated to the production efficiency, yield and productivity of 83.86%, 0.93 g/g and 3.49 g/L/h, respectively. The L-lactic acid production obtained from SSF was significantly improved when compared to TSF based on lower enzyme loading usage, shorter hydrolysis time and increase in production efficiency and productivity. Furthermore, there were no significant differences in the production by SSF between experiments conducted in laboratory bottle and 10-L fermenter. The results indicated the success of up-scaling for L-lactic acid production by SSF which could be developed for a further pilot-scale production of L-lactic acid.

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Construction of lactic acid-tolerant Saccharomyces cerevisiae by using CRISPR-Cas-mediated genome evolution for efficient D-lactic acid production.

Mitsui, R., Yamada, R., Matsumoto, T., Yoshihara, S., Tokumoto, H. & Ogino, H. (2020). Applied Microbiology and Biotechnology, 104(21), 9147-9158.

Lactic acid (LA) is chemically synthesized or fermentatively produced using glucose as substrate, mainly using lactic acid bacteria. Polylactic acid is used as a biodegradable bioplastic for packaging materials, medical materials, and filaments for 3D printers. In this study, we aimed to construct a LA-tolerant yeast to reduce the neutralization cost in LA production. The pHLA2-51 strain was obtained through a previously developed genome evolution strategy, and transcriptome analysis revealed the gene expression profile of the mutant yeast. Furthermore, the expression of the genes associated with glycolysis and the LA synthesis pathway in the LA-tolerant yeast was comprehensively and randomly modified to construct a D-LA-producing, LA-tolerant yeast. In detail, DNA fragments expressing thirteen genes, HXT7, HXK2, PGI1, PFK1, PFK2, FBA1, TPI1, TDH3, PGK1, GPM1, ENO2, and PYK2, and D-lactate dehydrogenase (D-LDH) from Leuconostoc mesenteroides were randomly integrated into the genomic DNA in the LA-tolerant yeast. The resultant engineered yeast produced about 33.9 g/L of D-LA from 100 g/L glucose without neutralizing agents in a non-neutralized condition and 52.2 g/L of D-LA from 100 g/L glucose with 20 g/L CaCO3 in a semi-neutralized condition. Our research provides valuable insights into non-neutralized fermentative production of LA.

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Production of a yeast-free focaccia with reduced salt content using a selected Leuconostoc citreum strain and seawater.

De Bellis, P., Montemurro, M., D'Imperio, M., Rizzello, C. G., Sisto, A. & Lavermicocca, P. (2020). LWT, 134, 109918.

A biotechnological protocol to produce a focaccia (a typical Italian flat bread) without bakers' yeast addition and with reduced salt was developed, to meet the current needs of the consumer. Based on its leavening capability, the Leuconostoc citreum strain C2.27 was selected to be used as a starter instead of the baker's yeast and inoculated in a liquid sourdough (type-II) for the production of the “yeast-free” focaccia. The addition of different NaCl concentrations and the replacement of the salt with food grade seawater were evaluated, and the capability of the selected strain to affect technological, nutritional and sensory features of the focaccia investigated. A significant improvement of the nutritional characteristics of the focaccia was observed compared to the control (leavened with bakers' yeast and added with NaCl 1.5 g/100 g) using 0.7 g/100 g of salt in the form of NaCl or seawater. Besides the reduced Na content (66% lower than the control), focaccia with seawater also showed a higher content of Ca2+ and Mg2+ (ca. 36% and 53%, respectively), and the lowest predicted glycemic index compared to the other experimental focaccia.

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Influence of the Microalga Chlorella vulgaris on the Growth and Metabolic Activity of Lactobacillus spp. Bacteria.

Ścieszka, S. & Klewicka, E. (2020). Foods, 9(7), 959.

The aim of this study was to evaluate the effect of the algae Chlorella vulgaris on the growth, acidifying activity, proportion of lactic acid isomers, and enzymatic profile of Lactobacillus brevis (ŁOCK 0944, ŁOCK 0980, ŁOCK 0992, and MG451814) isolated from vegetable silages. The results indicated that adding algae at concentrations of 0.1% (w/v) and 1.5% (w/v) to the Lactobacillus spp. growth medium accelerated the growth of bacteria and thus shortened their phase of logarithmic growth. The acidifying activity of the tested Lactobacillus brevis increased with an increased concentration of algae. Lactobacillus spp. cultured in the presence of Chlorella vulgaris showed higher production of L-lactic acid and lower D-lactic acid production. Moreover, the addition of algae changed the enzymatic activity of lactic acid bacteria; for instance, Lactobacillus brevis ŁOCK 0980 demonstrated more enzymatic activity of valine arylamidase, α-galactosidase, and α-glucosidase. Combining Lactobacillus brevis with the algae Chlorella vulgaris allows for the creation of innovative, functional products which confer favorable properties to the final product and open new horizons for the food industry.

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Portuguese cacholeira blood sausage: A first taste of its microbiota and volatile organic compounds.

Belleggia, L., Ferrocino, I., Reale, A., Boscaino, F., Di Renzo, T., Corvaglia, M. R., Cocolin, L., Milanović, V., Cardinali, F., Garofalo, C., Clementi, F., Aquilanti, L. & Osimani, A. (2020). Food Research International, 136, 109567.

Among typical Portuguese sausages, the cacholeira blood sausage undoubtedly represents one of the most popular preparations. To the authors’ knowledge, a lack of information on both the microbiota and the volatile organic compounds (VOCs) of this blood-containing sausage emerges from the available scientific literature. This study represents the first characterization of physico-chemical, microbiological and volatile traits of Portuguese cacholeira blood sausage. To this end, ready-to-eat cacholeira blood sausages were collected from two production batches manufactured in summer (batch 1) and autumn (batch 2). Viable counts showed active microbial communities mainly composed by lactic acid bacteria, coagulase negative cocci, enterococci and eumycetes. The metataxonomic approach showed a simple bacterial composition, which was dominated by Lactobacillus sakei in both the analyzed batches (1 and 2) considered. Carnobacterium, Enterococcus, Kluyvera, Lactococcus and Serratia were found as minor genera. The mycobiota varied according to the production season. Batch 1 was dominated by Starmerella apicola, Debaryomyces hansenii and Candida tropicalis, whereas batch 2 was dominated by D. hansenii. Moreover, Aspergillus spp., Kurtzmaniella zeylanoides, Saccharomyces cerevisiae, Kurtzmaniella santamariae, Brettanomyces bruxellensis and Pichia kluyveri were detected in both the batches as minority species. Seventy-two volatile compounds were identified, including esters, phenols, terpenoids, acids, alcohols, ketones, aldehydes, lactones, furans, sulphur and nitrogen compounds. Significant differences were seen in the amount of some compounds, as a feasible consequence of differences in the raw materials, artisan production and seasonality.

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Anticandidal activity of Lactobacillus spp. in the presence of galactosyl polyols.

Lipinska-Zubrycka, L., Klewicki, R., Sojka, M., Bonikowski, R., Milczarek, A. & Klewicka, E. (2020). Microbiological Research, 240, 126540.

Yeasts have a substantial impact on the contamination and loss of food. In this study, we applied bacteria of the genus Lactobacillus as natural biopreservatives. Anticandidal strains of bacteria were selected from among 60 strains of bacteria grown which were each with nine polyols or galactosyl polyols. Polyols and galactosyl polyols can act as prebiotics for lactic acid bacteria and can enhance the antifungal properties of bacteria by affecting their metabolism. The galactosyl polyols significantly improved the anticandidal activity of most of the bacteria we tested. Based on the screening, the most promising strains of bacteria were selected, and their metabolites (both primary and secondary) and enzymatic activity were characterized in the presence of polyols and galactosyl polyols. The qualitative and quantitative content of bacterial metabolites depended both on the bacterial strain and the type of culture medium. A wide variety of antifungals produced by bacteria, such as fatty acids, hydroxy fatty acids, and other acidic products with potential antagonistic activity (phenyllactic acid or hydroxyphenyllactic acid) were detected. The bacteria produced a high concentration of phenyllactic acid in the presence of galactosyl polyols (up to 84.3 mg/L). This finding could suggest that this metabolite may have a significant impact on the antifungal properties of lactobacilli against yeast. Galactosyl polyols influenced the enzymes involved in the synthesis of fatty acids and hydroxylated fatty acids (esterase lipase, acid phosphatase, and α-glucosidase). The mechanism of the antifungal effect of lactobacilli may be based on the synergistic effect of their primary and secondary metabolites, in particular phenyllactic acid.

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Dark fermentative hydrogen production from hydrolyzed sugar beet pulp improved by iron addition.

Cieciura-Włoch, W., Borowski, S. & Domański, J. (2020). Bioresource Technology, 314, 123713.

This study evaluated the impact of three different iron compounds (Fe2O3, FeSO4, FeCl3) on hydrogen production via mesophilic dark fermentation (DF) of hydrolyzed sugar beet pulp (SBP). In batch tests, the maximum hydrogen yield of over 200 dm3H2/kgVS was achieved with the addition of 0.1 gFe2O3/dm3, which was twice greater than the control. In semi-continuous experiments, the highest hydrogen production of 52.11 dm3H2/kgVS combined with 19.4 dm3CH4/kgVS methane yield was obtained at a dose of 1 gFe2O3/dm3. Acetic, lactic and caproic acids were the main metabolic products of DF. Microbiological studies showed some balance between hydrogen producing microorganisms from the order Clostridiales and lactic acid producers (LAB) affiliated with the orders Lactobacillales and Coriobacteriales. Moreover, the presence of methanogens affiliated to the genera Methanobrevibacter and Methanosphaera was also documented. An interesting finding was the appearance of rare bacteria from the genus Caproiciproducens, which was responsible for increased caproic acid production.

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Deciphering the D-/L-lactate-producing microbiota and manipulating their accumulation during solid-state fermentation of cereal vinegar.

Chai, L. J., Shen, M. N., Sun, J., Deng, Y. J., Lu, Z. M., Zhang, X. J., Shi, J. S. & Xu, Z. H. (2020). Food Microbiology, 92, 103559.

Symphony orchestra of multi-microorganisms characterizes the solid-state acetic acid fermentation process of Chinese cereal vinegars. Lactate is the predominant non-volatile acid and plays indispensable roles in flavor formation. This study investigated the microbial consortia driving the metabolism of D-/l-lactate during fermentation. Sequencing analysis based on D-/L-lactate dehydrogenase genes demonstrated that Lactobacillus (relative abundance: > 95%) dominated the production of both D-lactate and L-lactate, showing species-specific features between the two types. Lactobacillus helveticus (>65%) and L. reuteri (~80%) respectively dominated L- and D-lactate-producing communities. D-/L-lactate production and utilization capabilities of eight predominant Lactobacillus strains were determined by culture-dependent approach. Subsequently, D-/l-lactate producer L. plantarum M10-1 (d:l ≈ 1:1), L-lactate producer L. casei 21M3-1 (D:L ≈ 0.2:9.8) and D-/L-lactate utilizer Acetobacter pasteurianus G3-2 were selected to modulate the metabolic flux of D-/l-lactate of microbial consortia. The production ratio of D-/L-lactate was correspondingly shifted coupling with microbial consortia changes. Bioaugmentation with L. casei 21M3-1 merely enhanced L-lactate production, displaying ~4-fold elevation at the end of fermentation. Addition of L. plantarum M10-1 twice increased both D- and L-lactate production, while A. pasteurianus G3-2 decreased the content of D-/l-isomer. Our results provided an alternative strategy to specifically manipulate the metabolic flux within microbial consortia of certain ecological niches.

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Study of kefir drinks produced by backslopping method using kefir grains from Bosnia and Herzegovina: Microbial dynamics and volatilome profile.

Garofalo, C., Ferrocino, I., Reale, A., Sabbatini, R., Milanović, V., Alkić-Subašić, M., Boscaino, F., Aquilanti, L., Pasquini, M., Trombetta, M. F., Tavoletti, S., Coppola, R., Cocolin, L., Blesić, M., Sarić, Z., Osimani, A. & Osimani, A. (2020). Food Research International, 137, 109369.

Kefir is a well-known health-promoting beverage that can be produced by using kefir grains (traditional method) or by using natural starter cultures from kefir (backslopping method). The aim of this study was to elucidate the microbial dynamics and volatilome profile occurring during kefir production through traditional and backslopping methods by using five kefir grains that were collected in Bosnia and Herzegovina. The results from conventional pour plating techniques and amplicon-based sequencing were combined. The kefir drinks have also been characterized in terms of their physico-chemical and colorimetric parameters. A bacterial shift from Lactobacillus kefiranofaciens to Acetobacter syzygii, Lactococcus lactis and Leuconostoc pseudomesenteroides from kefir grains in traditional kefir to backslopped kefir was generally observed. Despite some differences within samples, the dominant mycobiota of backslopped kefir samples remained quite similar to that of the kefir grain samples. However, unlike the lactic acid and acetic acid bacteria, the yeast counts decreased progressively from the grains to the backslopped kefir. The backslopped kefir samples showed higher protein, lactose and ash content and lower ethanol content compared to traditional kefir samples, coupled with optimal pH values that contribute to a pleasant sensory profile. Concerning the volatilome, backslopped kefir samples were correlated with cheesy, buttery, floral and fermented odors, whereas the traditional kefir samples were correlated with alcoholic, fruity, fatty and acid odors. Overall, the data obtained in the present study provided evidence that different kefir production methods (traditional vs backslopping) affect the quality characteristics of the final product. Hence, the functional traits of backslopped kefir should be further investigated in order to verify the suitability of a potential scale-up methodology for backslopping.

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Challenges Associated with Byproducts Valorization-Comparison Study of Safety Parameters of Ultrasonicated and Fermented Plant-Based Byproducts.

Bartkiene, E., Bartkevics, V., Pugajeva, I., Borisova, A., Zokaityte, E., Lele, V., Sakiene, V., Zavistanaviciute, P., Klupsaite, D., Zadeike, D., Özogul, F, & Juodeikiene, G. (2020). Foods, 9(5), 614.

In order to promote the efficient use of byproducts from the production of plant-based beverages, which still contain a large amount of nutritional and functional compounds, microbiological and chemical safety characteristics should be evaluated and, if needed, improved. Many challenges are associated with byproducts valorization, and the most important ones, which should be taken into account at the further steps of valorization, are biological and chemical safety. For safety improving, several technological treatments (biological, physical etc.) can be used. In this study, the influence of low-frequency ultrasonication (US) and fermentation with Lactobacillus casei LUHS210 strain, as physical and biotechnological treatments, on the safety characteristics of the byproducts (BYs) from the processing of rice, soy, almond, coconut, and oat drinks was compared. Ultrasonication, as well as fermentation, effectively improved the microbiological safety of BYs. Ultrasonication and fermentation reduced the concentration of deoxynivalenol, on average, by 24% only in soy BYs. After fermentation, 15-acetyldeoxynivalenol was formed in all samples (<12 µg kg−1), except for soy BYs. The lowest total biogenic amines content was found in fermented rice BYs and ultrasonicated coconut BYs. When comparing untreated and fermented BYs, significant changes in macro- and micro-elements content were found. Ultrasonication at 37 kHz did not significantly influence the concentrations of macro- and micro-elements, while fermentation affected most of the essential micro-elements. Consequently, while ultrasonication and fermentation can enhance the safety of BYs, the specific effects must be taken into account on biogenic amines, mycotoxins, and micro and macro elements.

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The in vitro analysis of prebiotics to be used as a component of a synbiotic preparation.

Śliżewska, K. & Chlebicz-Wójcik, A. (2020). Nutrients, 12(5), 1272.

Prebiotics are food components that are selectively fermented by beneficial microbiota and which confer a health benefit. The aim of the study was to select a prebiotic for the chosen probiotic strains to create a synbiotic. The impact of prebiotics (inulin, maltodextrin, corn starch, β-glucan, and apple pectin) on five Lactobacillus spp. strains’ growth and metabolites synthesis (lactic, acetic, propionic, and butyric acids, ethanol, and acetaldehyde) was tested by the plate count method and by high-performance liquid chromatography, respectively. Moreover, the differences in the ratio of D(−) and L(+) lactate isomers produced by Lactobacillus spp., as well as variations in the probiotics’ enzymatic profiles associated with the prebiotic used for cultivation, were determined with a Megazyme rapid assay kit and API® ZYM assay, accordingly. Finally, the influence of the carbon source (prebiotic) used on the antagonistic activity of the probiotic strains towards pathogenic bacteria, such as Salmonella spp. Or Listeria monocytogenes was analyzed in the co-cultures. The results showed that the growth, metabolic profile, and antagonistic activity of the probiotics towards selected pathogens were the most favorable when 2% (w/v) of inulin was used. Therefore, the combination of inulin with selected probiotics is a promising synbiotic mixture.

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Effect of mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae on management of malolactic fermentation.

Russo, P., Englezos, V., Capozzi, V., Pollon, M., Segade, S. R., Rantsiou, K., Spano, G. & Cocolin, L. (2020). Food Research International, 134, 109246.

This work aims to improve the management of the malolactic fermentation (MLF) in red wines by elucidating the interactions between Starmerella bacillaris and Saccharomyces cerevisiae in mixed fermentations and malolactic bacteria. Two Starm. Bacillaris strains were individually used in mixed fermentations with a commercial S. cerevisiae. MLF was performed using two autochthonous Lactobacillus plantarum and one commercial Oenococcus oeni inoculated following a simultaneous (together with S. cerevisiae) or sequential (at the end of alcoholic fermentation) approach. The impact of yeast inoculation on the progress of MLF was investigated by monitoring the viable microbial populations and the evolution of the main oenological parameters, as well as the volatile organic composition of the wines obtained in mixed and pure micro-scale winemaking trials. Our results indicated that MLF was stimulated, inhibited, or unaffected in mixed fermentations depending on the strains and on the regime of inoculation. O. oeni was able to perform MLF under all experimental conditions, and it showed a minimal impact on the volatile organic compounds of the wine. L. plantarum was unable to perform MLF in sequential inoculation assays, and strain-depending interactions with Starm. Bacillaris were indicated as factor affecting the outcome of MLF. Moreover, uncompleted MLF were related to a lower aromatic complexity of the wines. Our evidences indicate that tailored studies are needed to define the appropriate management of non-Saccharomyces and malolactic starter cultures in order to optimize some technological parameters (i.e. reduction of vinification time) and to improve qualitative features (i.e. primary and secondary metabolites production) of red wines.

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Prebiotic Activity of Poly-and Oligosaccharides Obtained from Plantago major L. Leaves.

Lukova, P., Nikolova, M., Petit, E., Elboutachfaiti, R., Vasileva, T., Katsarov, P., Manev, H., Gardarin, C., Pierre, G., Michaud, P., Iliev, I. & Delattre, C. (2020). Applied Sciences, 10(8), 2648.

The aim of the present study was to evaluate the prebiotic potential of Plantago major L. leaves water-extractable polysaccharide (PWPs) and its lower molecular fractions. The structure of PWPs was investigated by high pressure anion exchange chromatography (HPAEC), size exclusion chromatography coupled with multi-angle laser light scattering detector (SEC-MALLS) and Fourier-transform infrared (FTIR) spectroscopy. The chemical composition and monosaccharide analyses showed that galacturonic acid was the main monosaccharide of PWPs followed by glucose, arabinose, galactose, rhamnose and xylose. FTIR study indicated a strong characteristic absorption peak at 1550 cm−1 corresponding to the vibration of COO group of galacturonic acid. The PWPs was subjected to hydrolysis using commercial enzymes to obtain P. major low molecular fraction (PLM) which was successively separated by size exclusion chromatography on Biogel P2. PWPs and PLM were examined for in vitro prebiotic activity using various assays. Results gave evidence for changes in optical density of the bacteria cells and pH of the growth medium. A heterofermentative process with a lactate/acetate ratio ranged from 1:1 to 1:5 was observed. The ability of PLM to stimulate the production of certain probiotic bacteria glycohydrolases and to be fermented by Lactobacillus sp. strains was successfully proved.

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Discovering microbiota and volatile compounds of surströmming, the traditional Swedish sour herring.

Belleggia, L., Aquilanti, L., Ferrocino, I., Milanović, V., Garofalo, C., Clementi, F., Cocolin, L., Mozzon, M., Foligni, R., Haouet, M. N., Scuota, S., Framboas, M. & Osimani, A. (2020). Food Microbiology, 91, 103503.

In this study, the microbiota of ready-to-eat surströmming from three Swedish producers were studied using a combined approach. The pH values of the samples ranged between 6.67 ± 0.01 and 6.98 ± 0.01, whereas their aw values were between 0.911 ± 0.001 and 0.940 ± 0.001. The acetic acid concentration was between 0.289 ± 0.009 g/100 g and 0.556 ± 0.036 g/100 g. Very low concentrations of lactic acid were measured. Viable counting revealed the presence of mesophilic aerobes, mesophilic lactobacilli and lactococci as well as halophilic lactobacilli and lactococci, coagulase-negative staphylococci, halophilic aerobes and anaerobes. Negligible counts for Enterobacteriaceae, Pseudomonadaceae and total eumycetes were observed, whereas no sulfite-reducing anaerobes were detected. Listeria monocytogenes and Salmonella spp. were absent in all samples. Multiplex real-time PCR revealed the absence of the bont/A, bont/B, bont/E, bont/F, and 4gyrB (CP) genes, which encode botulinic toxins, in all the samples analyzed. Metagenomic sequencing revealed the presence of a core microbiota dominated by Halanaerobium praevalens, Alkalibacterium gilvum, Carnobacterium spp., Tetragenococcus halophilus, Clostridiisalibacter spp. and Porphyromonadaceae. Psychrobacter celer, Ruminococcaceae, Marinilactibacillus psychrotolerans, Streptococcus infantis and Salinivibrio costicola were detected as minor OTUs. GC-MS analysis of volatile components revealed the massive presence of trimethylamine and sulphur compounds. Moreover, 1,2,4-trithiolane, phenols, ketones, aldehydes, alcohols, esters and long chain aliphatic hydrocarbons were also detected. The data obtained allowed pro-technological bacteria, which are well-adapted to saline environments, to be discovered for the first time. Further analyses are needed to better clarify the extent of the contribution of either the microbiota or autolytic enzymes of the fish flesh in the aroma definition.

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