D-Fructose/D-Glucose Assay Kit (Liquid Ready) 

The bioavailability of minerals, such as zinc and magnesium, has a significant impact on the fermentation process. These metal ions are known to influence the growth and metabolic activity of yeast, but there are few reports on their effects on lactic acid bacteria (LAB) metabolism during sour brewing. This study aimed to evaluate the influence of magnesium and zinc ions on the metabolism of Lactobacillus brevis WLP672 during the fermentation of brewers’ wort. We carried out lactic acid fermentations using wort with different mineral compositions: without supplementation; supplemented with magnesium at 60 mg/L and 120 mg/L; and supplemented with zinc at 0.4 mg/L and 2 mg/L. The concentration of organic acids, pH of the wort and carbohydrate use was determined during fermentation, while aroma compounds, real extract and ethanol were measured after the mixed fermentation. The addition of magnesium ions resulted in the pH of the fermenting wort decreasing more quickly, an increase in the level of L-lactic acid (after 48 h of fermentation) and increased concentrations of some volatile compounds. While zinc supplementation had a negative impact on the L. brevis strain, resulting in a decrease in the L-lactic acid content and a higher pH in the beer. We conclude that zinc supplementation is not recommended in sour beer production using L. brevis WLP672.

Plant-degrading enzymes can be produced by fungi on abundantly available low-cost plant biomass. However, enzymes sets after growth on complex substrates need to be better understood, especially with emphasis on differences between fungal species and the influence of inhibitory compounds in plant substrates, such as monosaccharides. In this study, Aspergillus niger and Trichoderma reesei were evaluated for the production of enzyme sets after growth on two “second generation” substrates: wheat straw (WS) and sugarcane bagasse (SCB). A. niger and T. reesei produced different sets of (hemi-)cellulolytic enzymes after growth on WS and SCB. This was reflected in an overall strong synergistic effect in releasing sugars during saccharification using A. niger and T. reesei enzyme sets. T. reesei produced less hydrolytic enzymes after growth on non-washed SCB. The sensitivity to non-washed plant substrates was not reduced by using CreA/Cre1 mutants of T. reesei and A. niger with a defective carbon catabolite repression. The importance of removing monosaccharides for producing enzymes was further underlined by the decrease in hydrolytic activities with increased glucose concentrations in WS media. This study showed the importance of removing monosaccharides from the enzyme production media and combining T. reesei and A. niger enzyme sets to improve plant biomass saccharification.

The strawberry tree (Arbutus unedo L.) fruits are used in small quantities for fresh consumption despite their excellent flavor. The aim of this work was to evaluate the storage ability of strawberry tree fruits for fresh consumption. Harvested fruits were stored in polystyrene foam trays covered with two film types: linear low density polyethylene of 10 µm thickness (PPL) or polyethylene film perforated with holes of 10 mm diameter spaced 50 mm (PP). Through 15 days storage at 0, 3 and 6°C, fruits were analyzed for quality parameters. The strawberry tree fruits presented relevant qualitative properties and were appreciated by panelists. Color parameters (L*, h°, C*) had higher decrease at 3 and 6°C than at 0°C. The Brix almost did not change and firmness decreased mainly in the first 4 days storage. Ethanol and weight loss increased with temperature mostly from 3 to 6°C. Strawberry tree fruits are a good source of ascorbic acid, glucose, fructose, anthocyanins and antioxidant activity. Those properties are maintained through 15 days storage at 0°C followed by 3°C. Film covers showed no significant differences between them. The temperature of 0°C was the best for preservation of fruit quality through 15 days shelf-life.