Novel inducers derived from starch for cellulase production by Trichoderma reesei

Soluble inducers derived from starch were investigated for cellulase production by T. reesei. Various methods of starch treatment were compared. Acid-hydrolysed starch was found to be most effective. When 1·0 g starch was employed for cellulase production, the cellulase so produced after 6 days of fermentation, with supplementation of 1% (0·01 ml/g paper) β-glucosidase, saccharified more than 15 g shredded waste office paper in 9·34% suspension, resulting in 10 g fermentable sugars, 72% of which was glucose. The effectiveness of the starch-derived inducers was compared with that of lactose, pure cellulose, CMC, xylan and prehydrolysate of pine wood. The effects of calcium chloride and sorbose addition on cellulase production, and the kinetics of cellulase production by the starch-derived inducers are presented.     

里氏木霉中纤维素酶的合成诱导及调控*

随着绿色化学的兴起,天然纤维素原料转化和利用的研究受到了高度重视和广泛应用。利用纤维素酶降解纤维素为燃料乙醇、生物柴油的生产铺设了道路。但纤维素酶的生产成本较高,限制了纤维素酶产业化应用。里氏木霉生产的纤维素酶组分丰富,是纤维素酶高产菌株,深入研究里氏木霉的纤维素酶诱导及表达调控机制,有助于提高其纤维素酶产率。近年来人们对里氏木霉的纤维素酶诱导过程和调控机制有了一定研究进展,综述了里氏木霉纤维素酶诱导和基因表达调控,首先介绍了纤维素、纤维二糖、槐糖、乳糖等几种诱导物及诱导物的转运蛋白,进一步综述了几种转录因子的调控作用,同时介绍了染色体调控、信号通路和光条件对纤维素酶诱导的影响。最后展望了未来里氏木霉纤维素酶诱导表达的研究方向,包括探明诱导物的本质及其具体过程、揭示转录因子之间的联系及转录调控网络、寻找信号转导关键功能蛋白及研究环境因素对纤维素酶的诱导作用等。     

Chitinolytic and chitosanolytic activities from crude cellulase extract produced by A. niger grown on apple pomace through Koji fermentation

Enzyme extracts of cellulase [filter paper cellulase (FPase) and carboxymethyl cellulase (CMCase)], chitinase, and chitosanase produced by Aspergillus niger NRRL-567 were evaluated. The interactive effects of initial moisture and different inducers for FP cellulase and CMCase production were optimized using response surface methodology. Higher enzyme activities [FPase 79.24+/- 4.22 IU/gram fermented substrate (gfs) and CMCase 124.04+/-7.78 IU/gfs] were achieved after 48 h fermentation in solid-state medium containing apple pomace supplemented with rice husk [1% (w/w)] under optimized conditions [pH 4.5, moisture 55% (v/w), and inducers veratryl alcohol (2 mM/kg), copper sulfate (1.5 mM/kg), and lactose 2% (w/w)] (p<0.05). Koji fermentation in trays was carried out and higher enzyme activities (FPase 96.67+/-4.18 IU/gfs and CMCase 146.50+/-11.92 IU/gfs) were achieved. The nonspecific chitinase and chitosanase activities of cellulase enzyme extract were analyzed using chitin and chitosan substrates with different physicochemical characteristics, such as degree of deacetylation, molecular weight, and viscosity. Higher chitinase and chitosanase activities of 70.28+/-3.34 IU/gfs and 60.18+/-3.82 to 64.20+/-4.12 IU/gfs, respectively, were achieved. Moreover, the enzyme was stable and retained 92-94% activity even after one month. Cellulase enzyme extract obtained from A. niger with chitinolytic and chitosanolytic activities could be potentially used for making low-molecular-weight chitin and chitosan oligomers, having promising applications in biomedicine, pharmaceuticals, food, and agricultural industries, and in biocontrol formulations.     

一株毛栓菌静置液体发酵产纤维素酶条件研究

考察一株新分离的毛栓菌静置产纤维素酶的条件,通过单因素试验和正交设计试验分别对培养基初始pH、培养基中的碳源、氮源及诱导物进行研究。利用DNS（3,5-二硝基水杨酸）法测定CMC-Na（羧甲基纤维素钠）纤维素酶活。结果表明：该毛栓菌静置发酵产纤维素酶的最适pH为5.0,最适碳源、氮源和诱导物分别是淀粉、酵母粉和干麸皮,且质量浓度分别为淀粉1%、酵母粉0.4%、干麸皮1.5%,在此条件下,进行静置发酵3d,可获得CMC-Na（羧甲基纤维素钠）纤维素酶活力最高为56.62U/mL。此研究开创了纤维素酶生产菌的新发现,与以往所报道的好氧产纤维素酶菌种黑曲霉、木霉等相比,具有发酵时间短、耗能小等优点,具有一定的潜在应用价值。