Abstract:

In order to isolate high efficient degumming strains from a ramie retting bacterial consortium RAMCD407, a specific solid medium mainly consisted of ramie gum materials from ramie retting liquids by RAMCD407 was utilized for strain screening and isolating. Biochemical methods combined with 16S rRNA gene sequencing and morphological discrimination were chosen for strain identification. Enzyme activity analysis and practical degumming experiments were adopted to test the potential of selected strains in ramie degumming industries. Two strains designated K30 and L11 were obtained after purification and screening. Both 2 strains can form hydrolysis halos either on the plate containing pectin or xylan. The pectinase activities were 238.47 U/mL for K30 and 170.79 U/mL for L11. The xylanase activities were 98.36 U/mL for K30 and 64.11 U/mL for L11. The residual gum contents of ramie fibers were reduced from 32.3% to 12.43% and 15.70%, respectively and the breaking strength of ramie fibers was all more than 5.5 cN/dtex, when K30 and L11 were used in ramie retting practice. VITEK testing and 16S rDNA sequencing consistently showed that K30 shared a 99% similarity with Bacillus subtilis and L11 shared a 99% similarity with Bacillus cereus.

Key words: ramie degumming, bacteria consortium, Bacillaceae, isolation, identification

摘要：

为了从苎麻脱胶共生菌群RAMCD407中分离高效脱胶菌种，利用苎麻发酵物培养基分离筛选高效脱胶菌株；形态、生化结合16S rDNA分子方法鉴定菌株；水解圈法结合酶活力测定验证入选菌株产酶能力；苎麻脱胶试验核实入选菌株脱胶能力；分离出K30和L11两个菌株。K30和L11都能在果胶和木聚糖平板上形成水解圈，K30的果胶酶和木聚糖酶活力分别为238.47 U/mL和 98.36 U/mL，L11的果胶酶和木聚糖酶活力分别为 170.79 U/mL和 64.11 U/mL；K30和L11进行苎麻生物脱胶时，能使纤维残胶率由32.3％下降为1243％和15.70％, 纤维强力均超过5.5 cN/dtex。VITEK系统生化鉴定和16S rDNA序列分析都一致表明，K30与枯草芽孢杆菌Bacillus subtilis相似性高达99％，L11与蜡样芽胞杆菌Bacillus cereus相似性达到99%。

关键词: 苎麻脱胶；共生菌群；芽孢杆菌；分离；鉴定