微生物および生化学技術ジャーナル

概要

Aerobic Conversion of Glycerol to 2,3-Butanediol by a Novel Klebsiella variicola SRP3 Strain

Md. Shafiqur Rahman, Zhongshun Yuan, Kesen Ma, Chunbao (Charles) Xu and Wensheng Qin

The manufacture of biodiesel generates about 10% crude glycerol as a core by- product. This research is to identify novel bacterial strains which are capable of efficiently converting glycerol aerobically, and improve the strains for large scale production of value-added products. The production of a major product 2,3-butanediol (2,3- BD) from glycerol as a sole carbon source by the newly isolated Klebsiella variicola SRP3 are reported in a series of batch processes under aerobic condition. This study also compares the bacterial cell biomass, bio-products and glycerol dehydrogenase (GDH) enzyme production of K. variicola SRP3 isolated from paper mill waste when grown in aerobic condition. The incubation temperature, pH, glycerol concentration and nitrogen sources are the most important factors ruling the glycerol dehydrogenase. Acidic initial pH (pH 5.0) led to enhanced GDH activity (558.2 μmol/min/mg protein), yielding 25.33 g/L 2,3-BD, 7.6 g/L 1,3-PDO and 2.2 g/L acetoin from 50.0 g/L glycerol. In our aerobic batch culture the mutated strain K. variicola SRM3 exhibited 1.3 fold increased GDH activity of 721.5 units/mg protein from 558.2 units/mg protein, yielding 29.87 g/L 2,3-BD, 7.08 g/L 1,3-PDO and 2.02 g/L acetoin from 50.0 g/L glycerol. In our report, the optimal conditions for maximal GDH enzyme activity were defined, and 0.79 g/g product yield was achieved by the muted strain K. variicola SRM3, which is the highest amount obtained from glycerol as a sole carbon source until now. The research has for the first time proved that this K. variicola species can efficiently convert glycerol.