NaCl-, protease-tolerant and cold-active endoglucanase from Paenibacillus sp. YD236 isolated from the feces of Bos frontalis.

Mingjie Dong,Nanyu Han,Junpei Zhou,Zunxi Huang,Yunjuan Yang,Junjun Li,Xianghua Tang,Bo Xu,Jidong Shen,Junmei Ding,Qian Wu,Yuelin Mu

doi:10.1186/s40064-016-2360-9

Abstract

Bos frontalis, which consumes bamboo and weeds, may have evolved unique gastrointestinal microorganisms that digest cellulase. A Paenibacillus sp. YD236 strain was isolated from B. frontalis feces, from which a GH8 endoglucanase gene, pglue8 (1107 bp, 54.5 % GC content), encoding a 368-residue polypeptide (PgluE8, 40.4 kDa) was cloned. PgluE8 efficiently hydrolyzed barley-β-d-glucan followed by CMC-Na, soluble starch, laminarin, and glucan from black yeast optimally at pH 5.5 and 50 °C, and retained 78.6, 41.6, and 34.5 % maximum activity when assayed at 20, 10, and 0 °C, respectively. Enzyme activity remained above 176.6 % after treatment with 10.0 mM β-mercaptoethanol, and was 83.0, 78, and 56 % after pre-incubation in 30 % (w/v) NaCl, 16.67 mg/mL trypsin, and 160.0 mg/mL protease K, respectively. Cys23 and Cys364 residues were critical for PgluE8 activity. pglue8, identified from B. frontalis feces for the first time in this study, is a potential alternative for applications including food processing, washing, and animal feed preparation.

Highlights

Cellulose is considered to be the most abundant renewable resource (Xiang et al 2014). β-Glucans, which are homopolymers of d-glucose linked by β-glycosidic bonds, commonly exist as cellulose in plants, the bran of cereal grains, and the cell walls of yeast, fungi, and bacteria (Na et al 2015)
The strain YD236 was classified into the genus Paenibacillus
Local BLAST analysis revealed that the gene pglue8 was homologous to the glycosyl hydrolase family 8 (GH8) enzyme

Summary

Introduction

Cellulose is considered to be the most abundant renewable resource (Xiang et al 2014). β-Glucans, which are homopolymers of d-glucose linked by β-glycosidic bonds, commonly exist as cellulose in plants, the bran of cereal grains, and the cell walls of yeast, fungi, and bacteria (Na et al 2015). Cellulose is solubilized by cellulases, which can be classified into the following three categories per catalytic mechanism: endoglucanase (E.C.3.2.1.4), exoglucanase (E.C.3.2.1.91) and β-glucosidase (E.C.3.2.1.21) (Javed et al 2009). Dong et al SpringerPlus (2016) 5:746 industries (MacDiarmid and Venancio 2006) These technologies have hardly been practically realized because of the high running cost and low enzyme yields (Li et al 2009; Limauro et al 2001; Ando et al 2002; Huang and Monk 2004; Ng et al 2009). Bos frontalis is one of the most precious and endangered species of wild animals in China. The genes encoding this cellulases in Bos frontalis have not been reported

Methods

Results

Conclusion