ε-Poly-L-lysine (ε-PL) is a secondary metabolite produced by Streptomyces albulus. It has a wide range of antibacterial activity, which makes it a higher safe new natural food preservative widely used in the food industry. However, there are some problems in the field of ε-PL production, such as difficult breeding of excellent strains. Metabolic engineering is an effective strategy to improve the yield of ε-PL and eventually enhancing its production. However, there were few studies on the key metabolic nodes and regulatory mechanisms of ε-PL biosynthesis. As a result, there is a lack of effective target genes used for metabolic engineering at present. In this study, five key genes involved in L-lysine biosynthesis pathway and the ε-PL synthase gene were picked out based on literatures mining, i.e. pyruvate carboxylase gene(pyc), phosphoenolpyruvate carboxylase gene(ppc), glucose-6-phosphate dehydrogenase gene(zwf), dihydropyridine dicarboxylate synthase gene(dapA), diaminopelate decarboxylase gene(lysA)and ε-PL synthase gene(pls). Overexpressing of these genes in S. albulus WG608 individually, and these parameters such as ε-PL production, the ε-PL production per unit cell and carbon source conversion ratios to were used to evaluate the validity of these genes. The effects of overexpressed strains with target genes were comprehensively investigated on ε-PL production at different levels such as shake flask fermentation, 1 L batch fermentation, and 5 L fed-batch fermentation. The results showed that overexpression of ppc, pyc and pls could effectively promoted the synthesis of ε-PL in S. albulus WG608. In the fed-batch fermentation, the yields of ε-PL in overexpressed strains OE-ppc, OE-pyc and OE-pls were increased by 2.8%, 9.9%, and 16.3%, respectively, compared with the original strain S. albulus WG608. Meanwhile, the ε-PL production per unit cell were increased by 12.7%, 21.8%, and 56.4%, respectively. In addition, glucose conversion ratios were also increased by 12.5%, 9.4%, and 23.0%, respectively, compared with the original strain S. albulus WG608. In order to evaluate the L-lysine utilization capacity of OE-pls, it was found that the yield of ε-PL increased by 81.9% when 4 g/L L-lysine was added at one time during batch fermentation in a 1 L fermenter. Then, the fed-batch fermentation of OE-pls strain was carried out in a 5 L fermenter for 192 h by continuous addition of L-lysine, the yield of ε-PL eventually reached 61.3 g/L. Meanwhile, the results showed that this strategy can not only improve the yield of ε-PL, but also significantly improve the conversion rate of carbon source. It was found that overexpression of pls combined with exogenous addition of L-lysine was an effective strategy to improve the production of ε-PL by S. albulus. The present research is helpful for further genetic manipulation on S. albulus to improve ε-PL production.
ZHANG Chongyang
,
YANG Hao
,
ZHU Daojun
,
LIU Tianyi
,
WANG Liang
,
ZHANG Hongjian
,
ZHANG Jianhua
,
CHEN Xusheng
. Effect of overexpression of key genes in L-lysine biosynthesis pathway and ε-poly-L-lysine synthase gene on ε-poly-L-lysine production[J]. Food and Fermentation Industries, 2023
, 49(6)
: 1
-9
.
DOI: 10.13995/j.cnki.11-1802/ts.031337
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