Improvement of cell growth and l-lysine production by genetically modified Corynebacterium glutamicum during growth on molasses

Abstract

Fructose-1,6-bisphosphatase (FBPase) and fructokinase (ScrK) have important roles in regenerating glucose-6-phosphate in the pentose phosphate pathway (PPP), and thus increasing L-lysine production. This article focuses on the development of L-lysine high-producing strains by heterologous expression of FBPase gene fbp and ScrK gene scrK in C. glutamicum lysC (fbr) with molasses as the sole carbon source. Heterologous expression of fbp and scrK lead to a decrease of residual sugar in fermentation broth, and heterologous expression of scrK prevents the fructose efflux. Heterologous expression of fbp and scrK not only increases significantly the activity of corresponding enzymes but also improves cell growth during growth on molasses. FBPase activities are increased tenfold by heterologous expression of fbp, whereas the FBPase activity is only increase fourfold during co-expression of scrK and fbp. Compared with glucose, the DCW of heterologous expression strains are higher on molasses except co-expression of fbp and scrK strain. In addition, heterologous expression of fbp and scrK can strongly increase the L-lysine production with molasses as the sole carbon source. The highest increase (88.4 %) was observed for C. glutamicum lysC (fbr) pDXW-8-fbp-scrK, but the increase was also significant for C. glutamicum lysC (fbr) pDXW-8-fbp (47.2 %) and C. glutamicum lysC (fbr) pDXW-8-scrK (36.8 %). By-products, such as glycerol and dihydroxyacetone, are decreased by heterologous expression of fbp and scrK, whereas trehalose is only slightly increased. The strategy for enhancing L-lysine production by regeneration of glucose-6-phosphate in PPP may provide a reference to enhance the production of other amino acids during growth on molasses or starch.

Enhanced l-lysine production from pretreated beet molasses by engineered Escherichia coli in fed-batch fermentation

“…The rates of sugar consumption, biomass growth, and L-lysine accumulation in the fermentation of L-lysine using untreated beet molasses were lower, when compared with those observed in L-lysine fermentation using other carbon sources. In previous studies, inefficient conversion of molasses had also been reported in the fermentation of L-lysine [4], pullulan [13], L-lactic acid [5]. However, several reports have proved that pretreatment could improve the fermentable properties of molasses, thereby increasing the sugar consumption rate and target product yield [5,15,[17][18][19].…”

“…Becker et al [10] and Ahmed et al [1] used metabolically engineered C. glutamicum and B. lactofermentum, respectively, to obtain high L-lysine yield, titer, and productivity only with a mixture of molasses and glucose. Xu et al [4] developed an L-lysine-producing engineered C. glutamicum strain that could utilize molasses (pretreated by filtration to remove suspended components) as a sole carbon source, but this strain still showed a longer lag phase and a slower sugar consumption rate [lower than 1 g/(L h)] in batch cultivation. Several studies have been conducted to develop sucrose-metabolizing E. coli strains using gene recombination technology to produce succinic acid [7], L-lactic acid [11], and benzaldehyde lyase [9] from molasses, the productivities, titer, yield, and biomass achieved using untreated molasses were significantly lower than those obtained using glucose or sucrose.…”

“…such as Escherichia coli [3]. Nevertheless, with the continuous expansion of the global market for L-lysine, less expensive fermentation substrates are needed to reduce the costs of production [4].…”

Overexpression of methionine adenosyltransferase in Corynebacterium glutamicum for production of S‐adenosyl‐l‐methionine

“…• C and shaking at 200 rpm for 72 H. The cells were harvested for enzyme activity analysis and SAM production. The dry cell weight (DCW) per liter of C. glutamicum was calculated according to formula: DCW = 0.34 × OD 562 [36].…”

Production of L-ornithine from sucrose and molasses by recombinant Corynebacterium glutamicum

“…In addition, sucrose has also a beneficial effect on protection of cells from oxidative, heat, and acids stresses, so it can be an appropriate carbon source to enhance bioproduct production. Molasses, a waste product of the sugar industry, is widely used for L-lysine (Xu et al 2013) and ethanol (Kopsahelis et al 2007(Kopsahelis et al , 2009) production by microbial fermentation. Molasses is a mixture of sugar, nonsugars, and water.…”