Improving xylose utilization of defatted rice bran for nisin production by overexpression of a xylose transcriptional regulator in Lactococcus lactis. (August 2017)

• Record Type: Journal Article
• Authors: Liu, Jiaheng; Ma, Zelin; Zhu, Hongji; Caiyin, Qinggele; Liang, Dongmei; Wu, Hao; Huang, Xu; Qiao, Jianjun
• Is Part Of: Bioresource technology. Volume 238(2017)
• Page Start: 690
• Page End: 697
• Publication Date: 2017-08
• Subjects: Defatted rice bran -- Nisin -- Lactococcus lactis -- Xylose utilization -- xylR; Biomass -- Periodicals; Biomass energy -- Periodicals; Bioremediation -- Periodicals; Agricultural wastes -- Periodicals; Factory and trade waste -- Periodicals; Organic wastes -- Periodicals; Bioénergie -- Périodiques; Déchets agricoles -- Périodiques; Déchets industriels -- Périodiques; Déchets organiques -- Périodiques; Déchets (Combustible) -- Périodiques; 662.88
• DOI: 10.1016/j.biortech.2017.04.076
• Languages: English
• ISSNs: 0960-8524

Abstract

Highlights: Defatted rice bran could substitute for refined sugars and partial peptone. Thermal-pretreatment followed by enzymatic hydrolysis retained soluble proteins. We reported low activity of XylR restricted xylose utilization of L. lactis . A novel strategy of XylR overexpression followed by adaptive evolution was proposed. HD medium supported higher nisin yield than sucrose medium. Abstract: Present investigation explores the potential of defatted rice bran (DRB) serving as sole carbon source and partial nitrogen source to support Lactococcus lactis growth and nisin production. To retain the nutrients in DRB, especially protein fractions, thermal pretreatment followed by enzymatic hydrolysis without washing step was applied for saccharification. A maximum of 45.64 g reducing sugar mainly containing 30.26 g glucose and 5.66 g xylose from 100 g DRB was attained in hydrolysates of DRB (HD). A novel strategy of xylR (xylose transcriptional regulator) overexpression followed by evolutionary engineering was proposed, which significantly increased the capacity of L. lactis to metabolize xylose. Subsequently, RT-PCR results indicated that xylR overexpression stimulated expression of xylose assimilation genes synergistically with exposure to xylose. In HD medium, the highest nisin titer of the engineered strain FEXR was 3824.53 IU/mL, which was 1.37 times of that in sucrose medium by the original strain F44.