title: Production of L-lactic acid by a thermophilic Bacillus mutant using sodium hydroxide as neutralizing agent.
abstract: A sodium lactate tolerant mutant strain named Bacillus sp. Na-2 was obtained and applied to sodium hydroxide-based L-lactic acid (LA) production process. The influences of aeration and pH were investigated to further improve the resistance of strain Na-2 against sodium lactate stress and to obtain the most efficient L-LA production process. Although mild aeration was favorable for cell growth and L-LA production, vigorous aeration resulted in a metabolic shift from homolactic to mixed-acid/acetoin fermentation. Therefore, a two-stage aeration control strategy was employed. Optimum pH was found to be 6.0. A total of 106.0 g/l L-LA was produced in 30 h by Bacillus sp. Na-2 using sodium hydroxide as neutralizing agent. Productivity, conversion rate and optical purity were 3.53 g/l/h, 94% and 99.5%, respectively. The remarkable fermentation traits of Bacillus sp. Na-2 and the environment-friendly characteristics of NaOH-based process represent new insight for industrial scale production of L-LA.
authors.affiliation: Institute for Stem Cells and Tissue Engineering, College of Pharmacy, Binzhou Medical University, Yantai, People's Republic of China.
authors.forename: Jiayang
authors.initials: J
authors.lastname: Qin
authors.forename: Xiuwen
authors.initials: X
authors.lastname: Wang
authors.forename: Zhaojuan
authors.initials: Z
authors.lastname: Zheng
authors.forename: Cuiqing
authors.initials: C
authors.lastname: Ma
authors.forename: Hongzhi
authors.initials: H
authors.lastname: Tang
authors.forename: Ping
authors.initials: P
authors.lastname: Xu
mesh_terms: D000332:Aerobiosis / Q000187:drug effects; D001407:Bacillus / Q000166:cytology / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*; D018533:Biomass; D017610:Calcium Compounds / Q000494:pharmacology; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007773:Lactates / Q000494:pharmacology; D019344:Lactic Acid / Q000096:biosynthesis*; D009154:Mutation / Q000235:genetics*; D010100:Oxygen / Q000494:pharmacology; D012972:Sodium Hydroxide / Q000494:pharmacology*; D019354:Sodium Lactate / Q000494:pharmacology; D013696:Temperature
chemical_list: D017610:Calcium Compounds; D007773:Lactates; C110051:calcium lactate; D019344:Lactic Acid; D012972:Sodium Hydroxide; D005947:Glucose; D010100:Oxygen; D019354:Sodium Lactate