title: D-lactic acid production by Sporolactobacillus inulinus Y2-8 immobilized in fibrous bed bioreactor using corn flour hydrolyzate.
abstract: In this study, a fibrous bed bioreactor (FBB) was used for D-lactic acid (D-LA) production by Sporolactobacillus inulinus Y2-8. Corn flour hydrolyzed with α-amylase and saccharifying enzyme was used as a cost-efficient and nutrient-rich substrate for D-LA production. A maximal starch conversion rate of 93.78% was obtained. The optimum pH for D-LA production was determined to be 6.5. Ammonia water was determined to be an ideal neutralizing agent, which improved the D-LA production and purification processes. Batch fermentation and fedbatch fermentation, with both free cells and immobilized cells, were compared to highlight the advantages of FBB fermentation. In batch mode, the D-LA production rate of FBB fermentation was 1.62 g/l/h, which was 37.29% higher than that of free-cell fermentation, and the D-LA optical purities of the two fermentation methods were above 99.00%. In fed-batch mode, the maximum D-LA concentration attained by FBB fermentation was 218.8 g/l, which was 37.67% higher than that of free-cell fermentation. Repeated-batch fermentation was performed to determine the long-term performance of the FBB system, and the data indicated that the average D-LA production rate was 1.62 g/l/h and the average yield was 0.98 g/g. Thus, hydrolyzed corn flour fermented by S. inulinus Y2-8 in a FBB may be used for improving D-LA fermentation by using ammonia water as the neutralizing agent.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing, 210009, P.R. China.
authors.forename: Ting
authors.initials: T
authors.lastname: Zhao
authors.forename: Dong
authors.initials: D
authors.lastname: Liu
authors.forename: Hengfei
authors.initials: H
authors.lastname: Ren
authors.forename: Xinchi
authors.initials: X
authors.lastname: Shi
authors.forename: Nan
authors.initials: N
authors.lastname: Zhao
authors.forename: Yong
authors.initials: Y
authors.lastname: Chen
authors.forename: Hanjie
authors.initials: H
authors.lastname: Ying
mesh_terms: D000641:Ammonia; D056449:Bacillales / Q000378:metabolism*; D019149:Bioreactors / Q000382:microbiology*; D002021:Buffers; D018914:Cells, Immobilized; D003470:Culture Media / Q000737:chemistry*; D005285:Fermentation; D005433:Flour; D006863:Hydrogen-Ion Concentration; D019344:Lactic Acid / Q000378:metabolism*; D003313:Zea mays
chemical_list: D002021:Buffers; D003470:Culture Media; D019344:Lactic Acid; D000641:Ammonia