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Kinetic modeling of biomass and lactic acid production by Enterococcus faecalis SLT13 have been developed during batch culture in M17 and Hydrolyzed Cheese Whey (HCW) in 2 L and 20 L bioreactors. The specific growth rate μmax was higher in 20 L bioreactor (1.09 h−1); however, the maximum specific lactic acid production rate qpmax and maximum specific sugar utilization rate qsmax were higher in 2 L bioreactor. Biomass and sugar utilization were affected by lactic acid inhibition in HCW. No effects of substrate inhibition have been observed. Substrate limitation of biomass has been observed on HCW in 20 L bioreactor; the substrate limitation constant for biomass Ksx was 4.229 g/L. Substrate limitation of sugar consumption has been observed on M17 in 2 L bioreactor; the substrate limitation constant for sugar consumption Kss was 2.73 g/L. Compared to experimental data, the model provided good predictions for biomass, sugar consumption, and lactic acid production. [ABSTRACT FROM AUTHOR]

The aim of this study was to develop a novel kefir beverage using date syrup, whey permeate, and whey. The levels of the kefir grain inoculum (2–5% w/v), fruit syrup (10–50% w/v), and whey permeate (0–5% w/v) on pH, total phenolic content, antioxidant activity, lactic acid bacteria and yeast counts, and overall acceptability were investigated using central composite design. The use of response surface methodology allowed us to obtain a formulation with acceptable organoleptic properties and high antioxidant activities. The obtained beverages had total phenolic content, % DPPH scavenging activity, and overall acceptability ranging from 24 to 74 mg GAE/mL, from 74.80 to 91.37 mg GAE/mL, and from 3.50 to 6 mg GAE/mL (based on a 1 to 9 preference scale), respectively. Date syrup of 36.76% (w/v), whey permeates of 2.99%, and kefir grains inoculum size of 2.08% were the optimized process conditions achieved. [ABSTRACT FROM AUTHOR]

The effect of controlled whey hydrolysis by papain on growth of two lactic acid bacteria isolated from artisanal Leben: Lactococcus lactis var. diacetylactis (SLT6 and SLT10) was investigated. The higher biomass and maximum specific growth rate ( μ) were obtained after 30 min of hydrolysis. HPLC analysis of peptides showed that whey hydrolysis reduced the amount of peptides of MW > 400 Da and increased those peptides of MW < 400 Da. The two studied strains exhibited different peptide requirements. The pH-controlled batch cultures in 30 min hydrolysed whey followed the Monod kinetic for growth and for lactate production. The values of the key kinetic constants were: maximum specific growth rate ( μ), 1.08 and 0.56 h; yield biomass on lactose ( Y), 0.20 and 0.18 g g and saturation constant K, 4.2 and 2.8 g L for SLT6 and SLT10, respectively. When compared with batch experimental data, the model provided good predictions for growth, lactose utilisation and lactate production profiles. [ABSTRACT FROM AUTHOR]