Selection of lactic acid bacteria for acidification of brown juice (grass juice), with the aim of making a durable substrate for L-lysine fermentation

BACKGROUND: Brown juice is a waste product from the green crop-drying industry. Heating and pressing of green crops prior to drying produces a juice rich in nutrients, which can be converted to a stable universal fermentation medium by lowering its pH to 4.0–4.5 via lactic acid fermentation. The aim of this study was to select a strain of lactic acid bacteria for industrial acidification of brown juice.RESULTS: Several strains were tested in fermentation experiments and Lactobacillus salivarius ssp. salivarius DSM 20555 was found to be the best choice.

It showed high growth rates at temperatures ranging from 40 to 48 °C, with an optimum temperature of 46 °C (µmax = 2.2 h−1), and maintained a high productivity at pH 4.0 in continuous fermentation. The highest productivity of 7.23 g L−1 h−1 was found at a dilution rate of 1.0 h−1.CONCLUSION: With today's increased focus on utilisation of residues from food and agro-industry, coupled with restrictions on their use as fertiliser for farmlands, lactic acid fermentation could play a significant role in conservation of these nutrient-rich liquids.

This study shows that Lb. salivarius ssp. salivarius DSM 20555 is a very promising micro-organism for use in such a process. Copyright © 2008 Society of Chemical Industry