title: An extremophile Microbacterium strain and its protease production under alkaline conditions.
abstract: Extremophiles are potential resources for alkaline protease production. In order to search for alkaline protease producers, we isolated and screened alkaliphilic microorganisms from alkaline saline environments. The microorganism HSL10 was identified as a member of the genus Microbacterium by morphological observation, Gram staining and sequence analysis of the 16S rRNA gene and the 16S-23S rRNA intergenic spacer region. By colony-forming unit counting under alkali or salt stress, it was further identified as an alkaliphilic microbe with mild halotolerance. In addition, it was capable of secreting alkaline proteases, evidenced by larger hydrolyzation zones in the skim milk-containing medium at pH 9.0 than at pH 7.0. Subsequently, we demonstrated that both NaCl and yeast extract significantly promoted protease production by HSL10. Finally, we established a sensitive colorimetric method for the detection of protease production by HSL10 under neutral and alkaline conditions, by using the Bradford reagent for substrate staining to improve the contrast between the hydrolyzation zone and the substrate background on agar plates. HSL10 was the first example of an alkaliphilic protease-producing member in Microbacterium, and its isolation and characterization have both academic and commercial importance.
authors.affiliation: The College of Life Sciences, Central China Normal University, Wuhan, China.
authors.forename: Jin
authors.initials: J
authors.lastname: Lü
authors.forename: Xiaodan
authors.initials: X
authors.lastname: Wu
authors.forename: Yali
authors.initials: Y
authors.lastname: Jiang
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Cai
authors.forename: Luyao
authors.initials: L
authors.lastname: Huang
authors.forename: Yongbo
authors.initials: Y
authors.lastname: Yang
authors.forename: Huili
authors.initials: H
authors.lastname: Wang
authors.forename: Aibing
authors.initials: A
authors.lastname: Zeng
authors.forename: Aiying
authors.initials: A
authors.lastname: Li
mesh_terms: D000192:Actinomycetales / Q000145:classification / Q000187:drug effects* / Q000201:enzymology* / Q000302:isolation & purification; D000468:Alkalies / Q000633:toxicity; D016000:Cluster Analysis; D015169:Colony Count, Microbial; D003124:Colorimetry / Q000379:methods; D003470:Culture Media / Q000737:chemistry; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004275:DNA, Ribosomal / Q000737:chemistry / Q000235:genetics; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D004783:Environmental Microbiology; D008853:Microscopy; D008969:Molecular Sequence Data; D010447:Peptide Hydrolases / Q000378:metabolism*; D010802:Phylogeny; D012336:RNA, Ribosomal, 16S / Q000235:genetics; D012492:Salts / Q000633:toxicity; D017422:Sequence Analysis, DNA
chemical_list: D000468:Alkalies; D003470:Culture Media; D004269:DNA, Bacterial; D004275:DNA, Ribosomal; D021903:DNA, Ribosomal Spacer; D012336:RNA, Ribosomal, 16S; D012492:Salts; D010447:Peptide Hydrolases
keywords: Alkaline protease; Extremophile; Microbacterium; Plate assay; Substrate staining