Jaeeun Song1, Su-Yeon Kim1, Dae-Hyuk Kim2, Young-Seok Lee1, Joon-Soo Sim1, Bum-Soo Hahn1, Chang-Muk Lee3. 1. Metabolic Engineering Division, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju, 54874, Republic of Korea. 2. Department of Molecular Biology, Institute for Molecular Biology and Genetics, Chonbuk National University, Jeonju, 54896, Republic of Korea. 3. Metabolic Engineering Division, National Institute of Agricultural Sciences, Rural Development Administration, Jeonju, 54874, Republic of Korea. changmuk@rda.go.kr.
Abstract
OBJECTIVE: Hermetia illucens is a voracious insect scavenger that efficiently decomposes food waste. To exploit novel hydrolytic enzymes from this insect, we constructed a fosmid metagenome library using unculturable H. illucens intestinal microorganisms. RESULTS: Functional screening of the library on carboxymethyl cellulose plates identified a fosmid clone with a product displaying hydrolytic activity. Fosmid sequence analysis revealed a novel mannan-degrading gene (ManEM17) composed of 1371 base pairs, encoding 456 amino acids with a deduced 54 amino acid N-terminal signal peptide sequence. Conceptual translation and domain analysis revealed that sequence homology was highest (46%) with endo-1,4-β-mannosidase of Anaerophaga thermohalophila. Phylogenetic and domain analysis indicated that ManEM17 belongs to a novel β-mannanase containing a glycoside hydrolase family 26 domain. The recombinant protein (rManEM17) was expressed in Escherichia coli, exhibiting the highest activity at 55 °C and pH 6.5. The protein hydrolyzed substrates with β-1,4-glycosidic mannoses; maximum specific activity (5467 U mg-1) occurred toward locust bean gum galactomannan. However, rManEM17 did not hydrolyze p-Nitrophenyl-β-pyranosides, demonstrating endo-form mannanase activity. Furthermore, rManEM17 was highly stable under stringent conditions, including polar organic solvents as well as chemical reducing and denaturing reagents. CONCLUSIONS: ManEM17 is an attractive candidate for mannan degradation under the high-organic-solvent and protein-denaturing processes in food and feed industries.
OBJECTIVE:Hermetia illucens is a voracious insect scavenger that efficiently decomposes food waste. To exploit novel hydrolytic enzymes from this insect, we constructed a fosmid metagenome library using unculturable H. illucens intestinal microorganisms. RESULTS: Functional screening of the library on carboxymethyl cellulose plates identified a fosmid clone with a product displaying hydrolytic activity. Fosmid sequence analysis revealed a novel mannan-degrading gene (ManEM17) composed of 1371 base pairs, encoding 456 amino acids with a deduced 54 amino acid N-terminal signal peptide sequence. Conceptual translation and domain analysis revealed that sequence homology was highest (46%) with endo-1,4-β-mannosidase of Anaerophaga thermohalophila. Phylogenetic and domain analysis indicated that ManEM17 belongs to a novel β-mannanase containing a glycoside hydrolase family 26 domain. The recombinant protein (rManEM17) was expressed in Escherichia coli, exhibiting the highest activity at 55 °C and pH 6.5. The protein hydrolyzed substrates with β-1,4-glycosidic mannoses; maximum specific activity (5467 U mg-1) occurred toward locust bean gum galactomannan. However, rManEM17 did not hydrolyze p-Nitrophenyl-β-pyranosides, demonstrating endo-form mannanase activity. Furthermore, rManEM17 was highly stable under stringent conditions, including polar organic solvents as well as chemical reducing and denaturing reagents. CONCLUSIONS: ManEM17 is an attractive candidate for mannan degradation under the high-organic-solvent and protein-denaturing processes in food and feed industries.
Authors: Thomas Klammsteiner; Andreas Walter; Tajda Bogataj; Carina D Heussler; Blaž Stres; Florian M Steiner; Birgit C Schlick-Steiner; Heribert Insam Journal: Front Microbiol Date: 2021-01-21 Impact factor: 5.640