title: A thermostable glucoamylase from Bispora sp. MEY-1 with stability over a broad pH range and significant starch hydrolysis capacity.
abstract: BACKGROUND
  Glucoamylase is an exo-type enzyme that converts starch completely into glucose from the non-reducing ends. To meet the industrial requirements for starch processing, a glucoamylase with excellent thermostability, raw-starch degradation ability and high glucose yield is much needed. In the present study we selected the excellent Carbohydrate-Activity Enzyme (CAZyme) producer, Bispora sp. MEY-1, as the microbial source for glucoamylase gene exploitation.
  
  
  RESULTS
  A glucoamylase gene (gla15) was cloned from Bispora sp. MEY-1 and successfully expressed in Pichia pastoris with a high yield of 34.1 U/ml. Deduced GLA15 exhibits the highest identity of 64.2% to the glucoamylase from Talaromyces (Rasamsonia) emersonii. Purified recombinant GLA15 was thermophilic and showed the maximum activity at 70°C. The enzyme was stable over a broad pH range (2.2-11.0) and at high temperature up to 70°C. It hydrolyzed the breakages of both α-1,4- and α-1,6-glycosidic linkages in amylopectin, soluble starch, amylose, and maltooligosaccharides, and had capacity to degrade raw starch. TLC and H1-NMR analysis showed that GLA15 is a typical glucoamylase of GH family 15 that releases glucose units from the non-reducing ends of α-glucans. The combination of Bacillus licheniformis amylase and GLA15 hydrolyzed 96.14% of gelatinized maize starch after 6 h incubation, which was about 9% higher than that of the combination with a commercial glucoamylase from Aspergillus niger.
  
  
  CONCLUSIONS
  GLA15 has a broad pH stability range, high-temperature thermostability, high starch hydrolysis capacity and high expression yield. In comparison with the commercial glucoamylase from A. niger, GLA15 represents a better candidate for application in the food industry including production of glucose, glucose syrups, and high-fructose corn syrups.
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Huifang
authors.initials: H
authors.lastname: Hua
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Huiying
authors.initials: H
authors.lastname: Luo
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Yingguo
authors.initials: Y
authors.lastname: Bai
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Kun
authors.initials: K
authors.lastname: Wang
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Canfang
authors.initials: C
authors.lastname: Niu
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Huoqing
authors.initials: H
authors.lastname: Huang
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Pengjun
authors.initials: P
authors.lastname: Shi
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Caihong
authors.initials: C
authors.lastname: Wang
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China; CAAS-ICRAF Joint Laboratory on Agroforestry and Sustainable Animal Husbandry, Beijing, 100193, P. R. China.
authors.forename: Peilong
authors.initials: P
authors.lastname: Yang
authors.affiliation: Key Laboratory for Feed Biotechnology of the Ministry of Agriculture, Feed Research Institute, Chinese Academy of Agricultural Sciences, Beijing, 100081, P. R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Yao
mesh_terms: D001203:Ascomycota / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D004795:Enzyme Stability; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D005087:Glucan 1,4-alpha-Glucosidase / Q000737:chemistry* / Q000235:genetics* / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D008969:Molecular Sequence Data; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D005656:Fungal Proteins; D005087:Glucan 1,4-alpha-Glucosidase