Cellulolytic enzymes in Microbulbifer sp. Strain GL-2, a marine fish intestinal bacterium, with emphasis on endo-1,4-β-glucanases Cel5A and Cel8.

IF 0.8 4区 生物学 Q4 BIOTECHNOLOGY & APPLIED MICROBIOLOGY
Ken-Ichiro Ohnishi, Seiya Watanabe, Aya Kadoya, Satoru Suzuki
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引用次数: 0

Abstract

Cellulose is an abundant biomass on the planet. Various cellulases from environmental microbes have been explored for industrial use of cellulose. Marine fish intestine is of interest as one source of new enzymes. Here, we report the discovery of genes encoding two β-glucosidases (Bgl3A and Bgl3B) and four endo-1,4-β-glucanases (Cel5A, Cel8, Cel5B, and Cel9) as part of the genome sequence of a cellulolytic marine bacterium, Microbulbifer sp. Strain GL-2. Five of these six enzymes (excepting Cel5B) are presumed to localize to the periplasm or outer membrane. Transcriptional analysis demonstrated that all six genes were highly expressed in stationary phase. The transcription was induced by cello-oligosaccharides rather than by glucose, suggesting that the cellulases are produced primarily for nutrient acquisition following initial growth, facilitating the secondary growth phase. We cloned the genes encoding two of the endo-1,4-β-glucanases, Cel5A and Cel8, and purified the corresponding recombinant enzymes following expression in Escherichia coli. The activity of Cel5A was observed across a wide range of temperatures (10-40 ˚C) and pHs (6-8). This pattern differed from those of Cel8 and the commercial cellulase Enthiron, both of which exhibit decreased activities below 30 ˚C and at alkaline pHs. These characteristics suggest that Cel5A might find use in industrial applications. Overall, our results reinforce the hypothesis that marine bacteria remain a possible source of novel cellulolytic activities.

海洋鱼类肠道细菌 Microbulbifer sp.菌株 GL-2 中的纤维素分解酶,重点是内-1,4-β-葡聚糖酶 Cel5A 和 Cel8。
纤维素是地球上一种丰富的生物质。人们一直在探索将环境微生物中的各种纤维素酶用于纤维素的工业用途。海洋鱼类肠道是新酶的一个有趣来源。在这里,我们报告发现了编码两种β-葡糖苷酶(Bgl3A 和 Bgl3B)和四种内切-1,4-β-葡聚糖酶(Cel5A、Cel8、Cel5B 和 Cel9)的基因,这些基因是纤维素分解海洋细菌 Microbulbifer sp.据推测,这六种酶中的五种(Cel5B除外)定位于外质或外膜。转录分析表明,所有这六个基因在静止期都高度表达。纤维素酶的转录是由纤维寡糖而不是葡萄糖诱导的,这表明纤维素酶的产生主要是为了在初始生长后获取营养,从而促进次生生长阶段。我们克隆了两种内-1,4-β-葡聚糖酶(Cel5A 和 Cel8)的编码基因,并在大肠杆菌中表达纯化了相应的重组酶。在很宽的温度范围(10-40 ˚C)和 pH 值范围(6-8)内都能观察到 Cel5A 的活性。这种模式与 Cel8 和商业纤维素酶 Enthiron 的模式不同,这两种酶在 30 ˚C 以下和碱性 pH 下的活性都会降低。这些特征表明,Cel5A 可用于工业应用。总之,我们的研究结果加强了这样一种假设,即海洋细菌仍然是新型纤维素分解活性的可能来源。
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来源期刊
Journal of General and Applied Microbiology
Journal of General and Applied Microbiology 生物-生物工程与应用微生物
CiteScore
2.40
自引率
0.00%
发文量
42
审稿时长
6-12 weeks
期刊介绍: JGAM is going to publish scientific reports containing novel and significant microbiological findings, which are mainly devoted to the following categories: Antibiotics and Secondary Metabolites; Biotechnology and Metabolic Engineering; Developmental Microbiology; Environmental Microbiology and Bioremediation; Enzymology; Eukaryotic Microbiology; Evolution and Phylogenetics; Genome Integrity and Plasticity; Microalgae and Photosynthesis; Microbiology for Food; Molecular Genetics; Physiology and Cell Surface; Synthetic and Systems Microbiology.
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