title: Bimutation breeding of Aspergillus niger strain for enhancing β-mannanase production by solid-state fermentation.
abstract: A parent strain Aspergillus niger LW-1 was mutated by the compound mutagenesis of vacuum microwave (VMW) and ethyl methane sulfonate (EMS). A mutant strain, designated as A. niger E-30, with high- and stable-yield β-mannanase was obtained through a series of screening. The β-mannanase activity of the mutant strain E-30, cultivated on the basic fermentation medium at 32°C for 96 h, reached 36,675 U/g dried koji, being 1.98-fold higher than that (18,50 1U/g dried koji) of the parent strain LW-1. The purified E-30 β-mannanase, a glycoprotein with a carbohydrate content of 19.6%, had an apparent molecular weight of about 42.0 kDa by SDS-PAGE. Its optimal pH and temperature were 3.5 and 65°C, respectively. It was highly stable at a pH range of 3.5-7.0 and at a temperature of 60°C and below. The kinetic parameters K(m) and V(max), toward locust bean gum and at pH 4.8 and 50°C, were 3.68 mg/mL and 1067.5 U/mg, respectively. The β-mannanase activity was not significantly affected by an array of metal ions and EDTA, but strongly inhibited by Ag(+) and Hg(2+). In addition, the hydrolytic conditions of konjak glucomannan using the purified E-30 β-mannanase were optimized as follows: konjak gum solution 240 g/L (dissolved in deionized water), hydrolytic temperature 50°C, β-mannanase dosage 120 U/g konjak gum, and hydrolytic time 8 h.
authors.affiliation: School of Medicine and Pharmaceutics, Jiangnan University, 1800 Lihu Road, Wuxi, Jiangsu 214122, PR China. biowmc@126.com
authors.forename: Minchen
authors.initials: M
authors.lastname: Wu
authors.forename: Cunduo
authors.initials: C
authors.lastname: Tang
authors.forename: Jianfang
authors.initials: J
authors.lastname: Li
authors.forename: Huimin
authors.initials: H
authors.lastname: Zhang
authors.forename: Jing
authors.initials: J
authors.lastname: Guo
mesh_terms: D001234:Aspergillus niger / Q000187:drug effects / Q000235:genetics* / Q000378:metabolism* / Q000528:radiation effects; D005020:Ethyl Methanesulfonate / Q000494:pharmacology; D005285:Fermentation / Q000187:drug effects / Q000235:genetics* / Q000528:radiation effects; D005818:Genetic Engineering / Q000379:methods*; D006031:Glycosylation / Q000187:drug effects / Q000528:radiation effects; D006868:Hydrolysis / Q000187:drug effects / Q000528:radiation effects; D008351:Mannans / Q000378:metabolism; D008872:Microwaves; D016296:Mutagenesis / Q000187:drug effects / Q000528:radiation effects; D009154:Mutation / Q000187:drug effects* / Q000528:radiation effects*; D044902:beta-Mannosidase / Q000096:biosynthesis* / Q000235:genetics / Q000378:metabolism
chemical_list: D008351:Mannans; C022901:(1-6)-alpha-glucomannan; D005020:Ethyl Methanesulfonate; D044902:beta-Mannosidase