Enhanced a novel β-agarase production in recombinant Escherichia coli BL21 (DE3) through induction mode optimization and glycerol feeding strategy

Agarases are hydrolytic enzymes that act on the hydrolysis of agar and have a broad range of applications in food, cosmetics and pharmaceutical industries. In this study, a glycerol feeding strategy based on induction mode optimization for high cell density and beta-agarase production was established, which could effectively control acetate yield. First, exponential feeding strategy of glycerol with different overall specific growth rates (mu) was applied in the pre-induction phase. The results showed that the low mu (mu=0.2) was suggested to be the optimal for cell growth and beta-agarase production. Second, the effects of induction temperature and the inducer concentration on cell growth and beta-agarase production were investigated in the post-induction phase. When induced by isopropyl-beta-d-thiogalactoside (IPTG), the strategy of 0.8 mmol/L IPTG induction at 20A degrees C was found to be optimal for beta-agarase production. When cultivation was induced by continuous lactose feeding strategy of 1.0 g/(L center dot h), the beta-agarase activity reached 112.5 U/mL, which represented the highest beta-agarase production to date. Furthermore, the beta-agarase was capable of degrading G. lemaneiformis powder directly to produce neoagarooligosaccharide, and the hydrolysates were neoagarotetraose (NA4) and neoagarohexaose (NA6). The overall research may be useful for the industrial production and application of beta-agarase.