Characterization of an L-arabinose isomerase from Bacillus coagulans NL01 and its application for D-tagatose production

Abstract

BackgroundL-arabinose isomerase (AI) is a crucial catalyst for the biotransformation of D-galactose to D-tagatose. In previous reports, AIs from thermophilic bacterial strains had been wildly researched, but the browning reaction and by-products formed at high temperatures restricted their applications. By contrast, AIs from mesophilic Bacillus strains have some different features including lower optimal temperatures and lower requirements of metallic cofactors. These characters will be beneficial to the development of a more energy-efficient and safer production process. However, the relevant data about the kinetics and reaction properties of Bacillus AIs in D-tagatose production are still insufficient. Thus, in order to support further applications of these AIs, a comprehensive characterization of a Bacillus AI is needed.ResultsThe coding gene (1422 bp) of Bacillus coagulans NL01 AI (BCAI) was cloned and overexpressed in the Escherichia coli BL21 (DE3) strain. The enzymatic property test showed that the optimal temperature and pH of BCAI were 60 °C and 7.5 respectively. The raw purified BCAI originally showed high activity in absence of outsourcing metallic ions and its thermostability did not change in a low concentration (0.5 mM) of Mn2+ at temperatures from 70 °C to 90 °C. Besides these, the catalytic efficiencies (kcat/Km) for L-arabinose and D-galactose were 8.7 mM-1 min-1 and 1.0 mM-1 min-1 respectively. Under optimal conditions, the recombinant E. coli cell containing BCAI could convert 150 g L-1 and 250 g L-1 D-galactose to D-tagatose with attractive conversion rates of 32 % (32 h) and 27 % (48 h).ConclusionsIn this study, a novel AI from B. coagulans NL01was cloned, purified and characterized. Compared with other reported AIs, this AI could retain high proportions of activity at a broader range of temperatures and was less dependent on metallic cofactors such as Mn2+. Its substrate specificity was understood deeply by carrying out molecular modelling and docking studies. When the recombinant E. coli expressing the AI was used as a biocatalyst, D-tagatose could be produced efficiently in a simple one-pot biotransformation system.Electronic supplementary materialThe online version of this article (doi:10.1186/s12896-016-0286-5) contains supplementary material, which is available to authorized users.

Heterologous expression and biochemical characterization of a thermostable xylulose kinase from Bacillus coagulans IPE22

“…As an important industrial strain, many enzymes were already cloned and characterized from B. coagulans , such as protease , carboxylesterase , arabinose isomerase , and xylanase . At present, only one xylulose kinase from B. coagulans has been cloned and purified from a lactic acid producer, B. coagulans NL01 .…”

Novel D-Galactose Isomerases from Lactobacillus Strains Isolated from the Sweet Sap of Agave atrovirens

“…L-arabinose is catabolized in grampositive bacteria through isomerization and converted into L-ribulose, which constitutes the first step in the catabolic pathway of L-arabinose (Lee et al, 2004;Xu et al, 2012;2013;2015). The same enzyme catalyzes the isomerization of D-galactose into D-tagatose (Zhang et al, 2007;Cheng et al, 2009;Mei et al, 2016). L-arabinose has been previously reported as the main inducer for the expression of the araA gene (Yanjun et al, 2011;Rhimi et al, 2011;Xu et al, 2013) and thus, the preferred carbon source for enrichment and selective media, to be used in a large scale screening for the detection and selection of novel bacterial isolates producers of D-GI.…”

Tagatose as a Potential Nutraceutical: Production, Properties, Biological Roles, and Applications

“…The biological conversion of d ‐galactose into d ‐tagatose by application of l‐ AI enzyme seems to be a viable process because it relies on isomerisation of d ‐galactose, an industrial by‐product of cheese industry (Torres, Manzo, Rubiolo, Batista‐Vieraa, & Mammarella, ). During the past few decades, biological production of d ‐tagatose has been studied using l‐ AI from E. coli (Yoon, Kim, & Oh, ), Lcatobacillus fermentum (Xu et al., ), Bacillus coagulans (Mei, Wang, Zang, Zheng, & Ouyang, ), Geobacillus thermodenitrificans (Kim & Oh, ), Geobacillus sterothermophilus (Lee et al., ), Thermotoga neapolitana (Kim et al., ), Thermotoga maritime (Lee et al., ), and Anoxybacillus flavithermus (Li, Zhu, Liu, & Sun, ). Different sources of l‐ AI and its properties are presented in Table .…”

“…Mostly, the expression of l-AI has been carried out in non-GRAS microorganism (Mei et al, 2016;Patel, Akhani, Patel, Dedania, & Patel, 2017), which is unsuitable for food and pharmaceutical applications owing to the safety concerns. Hence, researchers have attempted to express l-AI in GRAS microorganism such as Corynebacterium glutamicum, Bacillus sublilis, and Lactococcus lactis (Kim et al, 2012;Salonen, Salonen, Leisola, & Nyyssola, 2013).…”