Mannans are functional polysaccharides with unique biological activities that have been employed widely in food, medicine and pharmaceutics. Recent breakthroughs in plant polysaccharide metabolism identified numerous genes involved in the biosynthesis of mannans. However, constructing highly efficient low-cost microbial cell factories to produce low-molecular-weight (LMW) mannans remains challenging. In this work, we designed a de novo mannan synthetic pathway in food-grade Bacillus subtilis, resulting in mannan accumulation of 0.97 g/L. By co-expressing the identified committed genes (manC, manB, manA and pgi), mannan production was significantly increased to 2.5 g/L. Furthermore, by redirecting the carbon flux using a glucose-repressed promoter to control pfkA expression, mannan production was substantially increased to 4.1 g/L. Production was further enhanced to 12.6 g/L (average MW 6370 Da) in 3-L fed-batch fermentation. This work provides alternative synthetic pathways for metabolic engineering of LMW mannans in B. subtilis, and a useful, optimisable approach to enhance mannans production.
Bacillus subtilis, Metabolic engineering, De novosynthetic pathway, functional polysaccharide, low-molecular-weight mannan, redirecting carbon flux
NCBI PubMed ID: 33142650Publication DOI: 10.1016/j.carbpol.2020.117115Journal NLM ID: 8307156Publisher: Elsevier
Correspondence: jinpeng@zafu.edu.cn; qizhendu@163.com
Institutions: College of Agricultural and Food Sciences, Zhejiang A & F University, Hangzhou, 311300, China, Technology Center of Haikou Customs District China, Haikou 570311, China, Institute of Microbial Engineering, Henan University, Kaifeng, China
Methods: GC-MS, FTIR, biochemical methods, RT-PCR, glycoengineering, DNA manipulation, HPLC-GPC-RI, OD
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