Isolation of salt-tolerant Vibrio alginolyticus X511 for efficient co-production of 2,3-butanediol and alginate lyase from Laminaria japonica.

In order to establish an efficient microbial transformation platform based on seaweed feedstocks, experiments were performed to isolate a salt-tolerant strain capable of producing alginate lyase and 2,3-butanediol (2,3-BDO). Its physiological and biochemical characteristics, carbon source utilization, and product synthesis capabilities were investigated, and then the process for co-producing alginate lyase and 2,3-BDO from Laminaria japonica was optimized. Results showed that the isolated strain was identified as Vibrio alginolyticus, which was capable of utilizing multiple carbon sources to produce alginate lyase and 2,3-BDO even in the presence of 5 % NaCl. The highest reducing sugar yield was achieved as the Laminaria japonica pretreated with 1 % (v/v) sulfuric acid at 120 °C for 18 min. The enzymatic hydrolysis was boosted by devising a novel tween 80-assisted enzyme complex containing 60 FPU/g of cellulase, 15 U/g of pectinase, 20 U/g of alginate lyase, and 90 mg/g of tween 80. After establishing a semi-simultaneous saccharification and fermentation (S-SSF) strategy, the sugars could be fully utilized, yielding 14.83 g/L 2,3-BDO and 11.02 kU/L alginate lyase, respectively. Mass balance calculations indicating that up to 140 g of 2,3-butanediol and 120 kU of alginate lyase can be obtained from per kg of Laminaria japonica via this integrated approach.