Multi-strategy in production of high titer gluconic acid by the fermentation of concentrated cellulosic hydrolysate with Gluconobacter oxydans

Abstract

Cellulosic hydrolysate from the hydrolysis of glucan-riched biomass can offer abundantly bioavailable glucose, which is an alternative feedstock for gluconic acid production. In order to speed up the process of cellulosic-based gluconic acid synthesis industrialization, cost reduction by using efficient substrate in batch-fermentation with high yield and productivity is extremely important. However, enriched glucose obtained by concentrating enzymatic hydrolysate inevitably ascends the viscosity, resulting in a lower oxygen transfer rate that cannot meet the requirement of bio-oxidation with Gluconobacter oxydans , resulting in gluconic acid productivity decreased drastically once the glucose content in the concentrated enzymatic hydrolysate was over 240 g/L with corresponding viscosity over 4 mPa·s. In view of the above problems, a combined strategy of activated carbon treatment and high-tension oxygen supply was applied to improve efficiency. Finally, approximately 230 g/L gluconic acid with 9.6 g/L/h productivity was achieved, which enabled the industrial-scale gluconic acid bio-production from cellulosic materials . • COS-SSB system can efficiently enhance the oxygen transfer rate and productivity. • CEH contain 240 g/L glucose could be used for GA production after AC treatment. • 231 g/L GA with 9.6 g/L/h productivity was achieved in CEH by combined strategy.