Alternative Heterologous Expression of l-Arabinose Isomerase from Enterococcus faecium DBFIQ E36 By Residual Whey Lactose Induction

Abstract

This study reports an alternative strategy for the expression of a recombinant l-AI from Enterococcus faecium DBFIQ E36 by auto-induction using glucose and glycerol as carbon sources and residual whey lactose as inducer agent. Commercial lactose and isopropyl β-d-1-thiogalactopyranoside (IPTG) were also evaluated as inducers for comparison of enzyme expression levels. The enzymatic extracts were purified by affinity chromatography, characterized, and applied in the bioconversion of d-galactose into d-tagatose. l-AI presented a catalytic activity of 1.67 ± 0.14, 1.52 ± 0.01, and 0.7 ± 0.04 U/mL, when expressed using commercial lactose, lactose from whey, and IPTG, respectively. Higher activities could be obtained by changing the protocol of enzyme extraction and, for instance, the enzymatic extract produced with whey presented a catalytic activity of 3.8 U/mL. The specific activity of the enzyme extracts produced using lactose (commercial or residual whey) after enzyme purification was also higher when compared to the enzyme expressed with IPTG. Best results were achieved when enzyme expression was conducted using 4 g/L of residual whey lactose for 11 h. These results proved the efficacy of an alternative and economic protocol for the effective expression of a recombinant l-AI aiming its high-scale production. KeywordsCheese whey • l-Arabinose isomerase • Escherichia coli expression • d-Tagatose • Auto-induction * Denise Cavalcante Hissa

Characterization of a Metallic-Ions-Independent L-Arabinose Isomerase from Endophytic Bacillus amyloliquefaciens for Production of D-Tagatose as a Functional Sweetener

“…Hitherto, numerous microbial species were found to produce L-AI including such as Lactobacillus fermentum [31], Lactobacillus sakai 23 K [32], Klebsiella pneumoniae [33], Lactococcus lactis [34], Bacillus subtilis [35], Shewanella sp. [36], Enterococcus faecium [37], Clostridium hylemonae [26], Alicyclobacillus hesperidum URH17-3-68 [38], Anoxybacillus flavithermus [39], Arthrobacter sp. 22c [40], Bacillus thermoglucosidasius KCTC 1828 [41], Geobacillus stearothermophilus [42], Lactobacillus plantarum [43], Pediococcus pentosaceus PC-5 [44], Pseudoalteromonas haloplanktis ATCC 14,393 [45] and Shigella flexneri [46].…”