(623l) Construction of a Xylose-Induced System in Lactobacillus Brevis for Efficient Glutathione Production

Abstruct: Prioritization of sugar consumption is a common theme in bacterial growth. However, growth studies show that Lactobacillus brevis simultaneously consumes numerous carbon sources and appears to lack normal hierarchical control of carbohydrate utilization. Through this phenomenon, a new controlled expression system to target heterologous proteins to cytoplasm is described for Lactobacillus brevis CGMCC1306. It is based on the use of a xylose-inducible lactobacillus promoter, P_xylA. The capacities of this system to produce cytoplasmic was tested using a bifunctional glutathione synthetase gene (gshF) from Streptococcus thermophilus. Fermentation results showed that recombinant L. brevis CGMCC1306 (pNZ-P_xylA-gshF) harboring this system was able to accumulate GSH up to 36.9 mg/g cell dry weight in MRS medium with adding 10 g/L xylose and 0.6 g/L additional cysteine. Growth experiment with GFP as a reporter indicated that the induction of this system happened immediately in the present of xylose. These results confirm the potential of this expression system as an alternative and useful tool for the production of proteins of interest in L. brevis.