Enhanced biosynthesis and characterization of surfactin isoforms with engineered Bacillus subtilis through promoter replacement and Vitreoscilla hemoglobin co-expression. (July 2018)

• Record Type: Journal Article
• Authors: Wang, Qi; Yu, Huimin; Wang, Miaomiao; Yang, Huan; Shen, Zhongyao
• Is Part Of: Process biochemistry. Volume 70(2018)
• Page Start: 36
• Page End: 44
• Publication Date: 2018-07
• Subjects: Bacillus subtilis -- Promoter replacement -- Vitreoscilla hemoglobin -- Surfactin isoforms -- Surface activity; Biochemical engineering -- Periodicals; Biotechnology -- Periodicals; Biochemistry -- periodicals; Biotechnology -- periodicals; Chemical Engineering -- periodicals; Génie biochimique -- Périodiques; Biotechnologie -- Périodiques; Biochemical engineering; Biotechnology; Periodicals; 660.63
• DOI: 10.1016/j.procbio.2018.04.003
• Languages: English
• ISSNs: 1359-5113

Abstract

Graphical abstract: Highlights: An engineered Bacillus subtilis with high surfactin titer 10.2 g/L was constructed. Vitreoscilla hemoglobin co-expression successfully enhanced surfactin biosynthesis. Surfactin isoform C15 showed the best surface activity of the surfactin products. Abstract: The surfactin produced by Bacillus subtilis has great potential in enhanced oil recovery, agriculture and bio-mediation. Its further applications, however, are restrained by its low producing titer and the limited information about its isoforms. Using a strong IPTG-inducible promoter Pg3, the native promoter of surfactin synthase in wild-type B. subtilis THY-15 was replaced, which gave engineered THY-15/ Pg3-srfA . In a shaking flask, the surfactin titer of THY-15/ Pg3-srfA reached 8.2 g/L, significantly higher than 1.2 g/L of THY-15. In a 5-L fermenter, however, the surfactin titer of THY-15/ Pg3-srfA shrank to 5.6 g/L, which was later confirmed to be related to the low dissolved oxygen limit during fermentation. A Vitreoscilla hemoglobin (VHb) gene was then introduced into the engineered strain, obtaining a novel THY-15/ Pg3-srfA (VHb). Through the successful expression of VHb, the surfactin titer of THY-15/ Pg3-srfA (VHb) increased to 10.2 g/L in the flask and 8.6 g/L in the fermenter, for increases of 24% and 51%, respectively, compared with the non-VHb engineered strain. The contents, structures and surface activity of the surfactin isoforms produced by the engineered strains were further highlighted. Surfactin C15-isoform with 14.8 mg/L Critical Micelle Concentration, which can reduce surface tension of water to 27.1 mN/m (25 °C), is the most preferred.