title: Evaluation of commercial soy sauce koji strains of Aspergillus oryzae for γ-aminobutyric acid (GABA) production.
abstract: In this study, four selected commercial strains of Aspergillus oryzae were collected from soy sauce koji. These A. oryzae strains designated as NSK, NSZ, NSJ and NST shared similar morphological characteristics with the reference strain (A. oryzae FRR 1675) which confirmed them as A. oryzae species. They were further evaluated for their ability to produce γ-aminobutyric acid (GABA) by cultivating the spore suspension in a broth medium containing 0.4 % (w/v) of glutamic acid as a substrate for GABA production. The results showed that these strains were capable of producing GABA; however, the concentrations differed significantly (P < 0.05) among themselves. Based on the A. oryzae strains, highest GABA concentration was obtained from NSK (194 mg/L) followed by NSZ (63 mg/L), NSJ (51.53 mg/L) and NST (31.66 mg/L). Therefore, A. oryzae NSK was characterized and the sequence was found to be similar to A. oryzae and A. flavus with 99 % similarity. The evolutionary distance (K nuc) between sequences of identical fungal species was calculated and a phylogenetic tree prepared from the K nuc data showed that the isolate belonged to the A. oryzae species. This finding may allow the development of GABA-rich ingredients using A. oryzae NSK as a starter culture for soy sauce production.
authors.affiliation: Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
authors.forename: Safuan
authors.initials: S
authors.lastname: Ab Kadir
authors.affiliation: Fermentation Centre, Strathclyde Institute of Pharmacy and Biomedical Sciences, Strathclyde University, 161 Cathedral Street, Glasgow, G4 0RE, Scotland, UK.
authors.forename: Wan Abd Al Qadr Imad
authors.identifier: 0000-0002-5384-4325
authors.initials: WA
authors.lastname: Wan-Mohtar
authors.affiliation: Department of Bioprocess Technology, Faculty of Biotechnology and Biomolecular Science, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
authors.forename: Rosfarizan
authors.initials: R
authors.lastname: Mohammad
authors.affiliation: Department of Food Technology, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
authors.forename: Sarina
authors.initials: S
authors.lastname: Abdul Halim Lim
authors.affiliation: Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia.
authors.forename: Abdulkarim
authors.initials: A
authors.lastname: Sabo Mohammed
authors.affiliation: Department of Food Science, Faculty of Food Science and Technology, Universiti Putra Malaysia, 43400 UPM, Serdang, Selangor, Malaysia. nazamid@putra.upm.edu.my.
authors.forename: Nazamid
authors.initials: N
authors.lastname: Saari
mesh_terms: D001236:Aspergillus oryzae / Q000145:classification / Q000378:metabolism*; D005285:Fermentation; D018698:Glutamic Acid / Q000378:metabolism; D010802:Phylogeny; D045730:Soy Foods; D005680:gamma-Aminobutyric Acid / Q000096:biosynthesis*
chemical_list: D018698:Glutamic Acid; D005680:gamma-Aminobutyric Acid
keywords: Aspergillus oryzae; Fermentation; Glutamic acid; Soy sauce; γ-Aminobutyric acid