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CitST is a typical two-component regulatory system that can regulate citrate utilization and is involved in the regulation of carbohydrate metabolism in Bacillus subtilis. B. subtilis is a kind of dominant species to bio-degum ramie fibers, which could degrade and utilize non-cellulose components as a carbon source during bio-degumming. This study aimed to explore the regulatory function of response regulator CitT from CitST two-component system when B. subtilis was used for extracting ramie fibers. The results showed that gene knocked-out of citT could significantly decrease the bio-degumming ability of B. subtilis. The enzymatic activity mensuration of functional enzymes revealed that deficient in CitT would remarkably reduce the enzymatic activity of pectinase, but there was a little difference in transcriptional levels of their encoding genes with qRT-PCR analysis, which further demonstrated that it was a lack of correlation between mRNA expression and enzymatic activities. The data also reflected that CitT specifically regulated the pectin degradation in bio-degumming of ramie fibers by analyzing the polysaccharide degradation rates of gum components. In conclusion, it was shown for the first time that CitT probably positively regulated the bio-degumming of ramie fibers and was an important regulator in pectin degradation. [ABSTRACT FROM AUTHOR]

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Microbial treatment of natural fibers is a preferred alternatives in ramie degumming process as compared to conventional chemical degumming technology with alkaline treatment at high temperature. Usually, it is difficult to degrade the noncellulosic components of ramie bast completely with a single strain in the mono-culturing degumming system. Microbial coculture strategy has been widely used in biotechnology, especially in the degradation of biological materials. In the present study, five strains for ramie degumming were identified as Dickeya dadantii strain DCE-01, Bacillus subtilis strain 1101, Bacillus sp. B6, Bacillus cereus strain B7, and Bacillus cereus strain B8 by sequencing of 16 S rRNA genes. Enzymatic activities characterization, ramie degumming experiments with mono-culturing systems, and the evaluation of strain compatibility showed that group DCE-01/B7 were the most suitable pairs for the construction of bacterial coculturing system. After preliminary optimization of coculturing fermentation condition, the weight loss weight ratio of ramie fibers was 27%, which was increased 13.6% and 8.9% while compared to mono-culturing systems of strain B7 and DCE-01 respectively. These data highlighted the benefit of microbial coculture strategy in the application of ramie degumming process, and indicated a higher-efficiency alternative for the microbial degumming in the textile industry. [ABSTRACT FROM AUTHOR]

Degumming is the most important step before kenaf bast fibers used in textile industry. Microbial degumming is an environmental protection and energy-saving technology to replace the conventional chemical degumming. Higher efficiency strains are the essential prerequisite to promote the application of microbial degumming technology. Generally, the screening and evaluation of strains for kenaf bast degumming were based on activity of functional enzymes produced by microorganism. In order to investigate the relationship between enzymatic activity and effect of kenaf bast degumming, strains DCE-01, 1101, B6, B7, and B8 were incubated in pure cultured, sterilized and non-sterilized degumming systems. After culturing for 16 h, functional enzymes for kenaf bast degumming (such as pectinase, neutral protease, xylanase, β-mannanase, laccase, lignin peroxidase and manganese peroxidase) were detected in the supernatant, and degumming effect of kenaf bast under sterilized and non-sterilized systems were evaluated respectively. Results revealed that strain DCE-01 was the best for kenaf bast degumming, though its enzymatic activity was not the highest among five strains. And the pretreatment of kenaf bast by high-pressure-steam sterilization could promote the degumming effect. This study suggested that there were limitations when screening or evaluating high-efficient strains for kenaf bast degumming with the guidance of enzymatic activity. [ABSTRACT FROM AUTHOR]

Kenaf is one of the most important natural fiber crops. Traditional degumming with water retting causes serious environmental pollution and reduces the quality of fiber products. The development of kenaf industry is hindered by high production cost. Microbial degumming is suitable for kenaf bast degumming because of its high efficiency, energy conservation, low pollution, and high quality, among others. Through enrichment and screening from water sample, soil sample, and humus sample, we concentrated and identified 92 bacterial strains that could degrade kenaf bast colloid. The strains belonged to 11 genera and 16 species. Five of these strains did not produce cellulase and the weight loss rate of the kenaf bast fiber raw material was more than 20%. These strains belonged to Bacillus subtilis, Paenibacillus polymyxa, Clostridium acetobutylicum, Bacillus alcalophilus, and Erwinia chrysanthemi and were assigned with serial numbers from K1-K5, respectively. This study is the first to report the function of Bacillus pumilus, B. alcalophilus, Clostridium tertium, Brevibacillus brevis, Pectobacterium carotovora, E. chrysanthemi, and Tyromyces subcaesius in kenaf bast degumming. Pectinase and mannanase were the key enzymes in the degumming of kenaf bast. [ABSTRACT FROM AUTHOR]