Production of nisin from Lactococcus lactis in acid-whey with nutrient supplementation

The production of Nisin, an FDA-approved food preservative, was attempted by Lactococcus lactis subsp. lactis ATCC® 11454 using the underutilized milk industry effluent, acid-whey, as a substrate. Nisin production was further improved by studying the effect of supplementation of nutrients and non-nutritional parameters. The addition of yeast extract (6% w/v) as nitrogen source and sucrose (4% w/v) as carbon source were found to be suitable nutrients for the maximum nisin production. The changes in the medium pH due to lactic acid accumulation during batch fermentation and its influence on the production of nisin were analyzed in the optimized whey medium (OWM). The production characteristics in OWM were further compared with the nisin production in MRS media. The influence of nisin as an inducer for its own production was also studied and found that the addition of nisin at 0.22 mg/ml promote the nisin production. The analysis of consumption of various metal ions present in the OWM during the nisin production was also analyzed, and found that the copper ions are the most consumed ion. The highest nisin yield of 2.6 × 105 AU/mL was obtained with OWM.

Pulsed electric field effects on inactivation of microorganisms in acid whey

Prospects of pulsed electric field technology application on acid whey concentrate pretreatment were analyzed. Stationary and flow pre-treatment systems were combined with different treatment parameters: electric field strength (E = 39 kV/cm, 95 kV/cm, 92 kV/cm), pulse duration (τ = 60 ns, 90 ns, 1000 ns) and pulse number (pn = up to 100 pulses). Isolates of Saccharomyces sp. and Lactobacillus sp. were predominant in concentrate. Significant non-thermal inactivation effect was achieved after PEF treatment. Exposure to short pulses selectively inactivated yeast cells, as a result PEF technology can be applied for low-energy acid whey processing.