Efficient cellulose solubilization by a combined cellulosome-β-glucosidase system

The cellulosome, the multienzyme complex of the cellulase system ofClostridium thermocellum, that mediates the solubilization of insoluble cellulose, is strongly inhibited by the major end product, cellobiose. By combining a purified β-glucosidase fromAspergillus niger with the cellulosome, accumulated cellobiose was hydrolyzed thereby resulting in a dramatic enhancement (up to 10-fold) of cellulose degradation. The observed enhancement was expressed both in the rate and degree of solubilization of microcrystalline cellulose, compared with that observed for the unsupplemented cellulosome. Near-complete conversion of cellulose to glucose could be obtained from dense substrate suspensions (up to at least 200 g/L).     

The Clostridium cellulovorans cellulosome: an enzyme complex with plant cell wall degrading activity

Cellulose comprises a major portion of biomass on the earth, and the turnover of this material contributes to the CO2 cycle. Cellulases, which play a major role in the turnover of cellulosic materials, have been found either as free enzymes that work synergistically, or as an enzyme complex called the cellulosome. This review summarizes some of the general properties of cellulosomes, and more specifically, the properties of the Clostridium cellulovorans cellulosome. The C cellulovorans cellulosome is an extracellular enzyme complex with a molecular weight of about 1 x 10(6), and is comprised of at least ten subunits. The major subunit is the scaffolding protein CbpA, with a molecular weight of 189,000. This nonenzymatic subunit contains a cellulose binding domain (CBD) that binds the cellulosome to the substrate, nine conserved cohesins or enzyme binding domains, and four conserved surface layer homologous (SLH) domains. It is postulated that the SLH domains help to bind the cellulosome to the cell surface. The cellulosomal enzymes include cellulases (family 5 and 9 endoglucanases and a family 48 exoglucanase), a mannanase, a xylanase, and a pectate lyase. The cellulosome is capable of converting Arabidopsis and tobacco plant cells to protoplasts. One of the endoglucanases, EngE, contains three tandemly repeated SLHs at its N-terminus, and therefore appears capable of binding to the scaffolding protein CbpA as well as to the cell surface. Cellulosomes can attack crystalline cellulose, but the free cellulosomal enzymes can attack only soluble and amorphous celluloses. Nine genes for the cellulosome are found in a gene cluster cbpA-exgS-engH-engK-hbpA-engL-manA-engM-engN. Other cellulosomal genes such as engB, engE, and engY are not linked to the major gene cluster or to each other. By determining the structure and function of the cellulosome, we hope to increase the efficiency of the cellulosome by genetic engineering techniques.     

Continuous production of butanol by clostridium acetobutylicum immobilized in a fibrous bed bioreactor

We explored the influence of dilution rate and pH in continuous cultures of Clostridium acetobutylicum. A 200-mL fibrous bed bioreactor was used to produce high cell density and butyrate concentrations at pH 5.4 and 35°C. By feeding glucose and butyrate as a cosubstrate, the fermentation was maintained in the solventogenesis phase, and the optimal butanol productivity of 4.6g/(L h) and a yield of 0.42 g/g were obtained at a dilution rate of 0.9h⁻¹ and pH 4.3. Compared to the conventional acetone-butanol-ethanol fermentation, the new fermentation process greatly improved butanol yield, making butanol production from corn an attractive alternative to ethanol fermentation.     

The Anti-Inflammatory Activities of Fermented Curcuma That Contains Butyrate Mitigate DSS-Induced Colitis in Mice

Inflammatory bowel disease is characterized by a radical imbalance of inflammatory signaling pathways in the gastrointestinal tract, and it is categorized into two diseases, such as Crohn’s disease and ulcerative colitis. In this study, we investigated anti-inflammatory activities using fermented Curcuma that contains butyrate (FB). Nitric oxide production in RAW 264.7 cells and the expression of inducible nitric oxide synthase in the intestinal mucosa appears to be enhanced in active ulcerative colitis. Here, the cytotoxicity, physiological activity, and anti-inflammatory efficacy of FB in colitis animals were investigated. To verify the anti-inflammatory effect, this study was conducted using the dextran sulfate sodium (DSS)-induced colitis mice model. As a result, non-toxicity was confirmed, and anti-inflammatory effects were revealed by inducing a reduction of LPS-induced NO production. In the DSS-induced colitis, reduced weight was recovered and a decrease in inflammatory factors Ig-E and TNF-α in the mesenteric lymph node (MLN) and spleen was induced, and it was confirmed to help with the morphological remodeling of the intestine. In conclusion, this paper suggests that FB can help to alleviate intestinal inflammation and to improve the intestinal environment, with the help of morphological remodeling.     

Cloning and expression of aClostridium thermocellum dna fragment that encodes a protein related to cellulosome component sL

Antibodies raised against the SL subunit of the Clostridium thermocellum cellulosome were used to screen a library of C. thermocellum chromosomal DNA fragments constructed in the vector lambda gt11. A DNA fragment that encoded a polypeptide that crossreacted with the anti-SL antibodies was isolated and its restriction map elucidated. No similarity with other previously cloned DNA fragments has been found. The anti-SL crossreacting polypeptide was isolated from recombinant Escherichia coli and found to have a mol mass of 37,000 Da and to possess low levels of CMCase and Avicelase activity. Using CMC as the substrate, a temperature optimum of 55 degrees C and a pH optimum of 6.6 were observed. These properties were compared to those of C. thermocellum SL isolated by electroelution from an SDS gel, which was also found to possess low levels of CMCase and Avicelase activities. In addition, the SL proteins produced in C. thermocellum and E. coli were able to interact positively against Avicel with an endoglucanase (Ss) purified from the C. thermocellum crude cellulase preparation, and with a recombinant protein that crossreacted with anti-Ss antibodies.     

一种丁酸梭菌与鼠李糖乳杆菌的混合培养方法

采用混合培养的方法,通过CBS混合培养基,在37℃条件下,对丁酸梭菌与鼠李糖乳杆菌进行了混合培养.试验结果显示,两者在混合培养体系中表现出良好的互惠共生关系,混合培养生物量分别可达6.3×10~8,43.5×10~8 CFU/mL.较纯培养生物量分别增加80%和51.7%;混合培养液较纯培养对常见肠道致病菌具有更强的抑菌活性,抑菌活性大小依次为大肠杆菌,痢疾志贺氏菌,沙门氏菌.实验表明,该方法具有较好的可行性和实用性.