Rut C30 Research Articles

Utilization of potato pulp from potato starch processing

Potato pulp consisting of pectins, starch, cellulose and hemicellulose was separated by treatment with dilute sulphuric acid into pectins and starch on the one hand and cellulose and hemicellulose on the other. Pectins and starch were separated by fractional precipitation with methanol or acetone. The pulp residue (PR) consisting of hemicellulose and cellulose was enzymatically converted to glucose and xylose and fermented by Pachysolen tannophilus to produce ethanol. The PR and the residue of the enzymatic decomposition (RES) were used as substrates for enzyme production by Trichoderma reesei Rut C30 and Trichoderma reesei MGC 77 in batch and continuous cultures. The highest specific enzyme activities (6·1 U mg −1 avicelase, 23·4 U mg −1 CMC-ase and 66·8 U mg −1 xylanase) and productivities (8·9 U litre −1 h −1 avicelase, 34·3 U litre −1 h −1 CMC-ase and 97·8 U litre −1 h −1 xylanase) were obtained with RES in batch cultures. The enzyme mixture in the cultivation medium was concentrated by UF membrane treatment and diafiltration. The product quality was comparable with commercially available cellulases. The economy of the upgrading process is mainly influenced by the utilization of pectins, starch, and enzymes. Ethanol production from the hydrolysate of cellulose/hemicellulose is not economic because of the low sugar concentration in the hydrolysate.

Cellulase activity of a thermotolerant Aspergillus niveus isolated from desert soil

Nine strains of Aspergillus were isolated from desert soils in Iraq. The thermotolerant Aspergillus niveus RMF 7883 was found to possess a highly active cellulolytic system. Filter-paper degrading activity was 14·5 IU ml −1 whilst the activities of β-glucosidase and endoglucanase were 37 and 326 IU ml −1 respectively. The enzyme degraded cotton in 2–4 h and was stable for 5 months at −18° and +4°. This organism was a hyperproducer of β-glucosidase in comparison with Trichoderma reesei Rut C30, and appears to be a promising strain for the production of a highly active, thermotolerant and stable cellulolytic preparation.

Use of surface‐immobilized Trichoderma in batch and fed‐batch fermentations

Needle-punch polyester was shown to be an effective support material for the immobilization of Trichoderma reesei Rut C30. When used as a resident inoculum for a batch process, the immobilized Trichoderma was very stable and resulted in a reduced rate of biomass generation in the bulk liquid phase as compared to cultures inoculated with free mycelium. Fed-batch fermentations with the immobilized Trichoderma produced ca. 80% of the activity of those using free cells; however, the activity was more stable and the crude enzyme broth produced had a greatly reduced biomass concentration.

Cellulase screening by iodine staining: An artefact

Hydrolysis zones visualized by iodine ( KI/I 2 ) staining of cellulose-agar media after growth of Trichoderma reesei QM6a, RUT C30, QM9136 ( cellulase negative) or Thielavia terrestris cultures, or incubation of crude endoglucanases and amylases, were due primarily to degradation of a small amount of starch contaminant in commercial agar and not to cellulolysis as recently suggested. No zones were evident when amylase-digested agar or Gelrite was used as the gelling agent or when purified cellobiohydrolase and endoglucanase were used. Cellulase screening free from artefacts is best obtained by growing cultures on acid-swollen or crystalline cellulose with Gelrite as optimal gelling agent, followed by incubation at elevated temperature to enhance visualization of hydrolysis zones while restricting fungal growth, but without additional staining.

Effect of media composition and growth conditions on production of cellulase and β-glucosidase by a mixed fungal fermentation

The effect of growth temperature, medium composition and pH were examined in shake-flask-scale studies to determine the optimum conditions for cellulase production in mixed cultures of Trichoderma reesei Rut C30 and Aspergillus phoenicis. The optimum temperature and pH were 27°C and pH 4.6. Decreases in medium complexity and cost were achieved through reductions in the concentration of Ca, Mg, and K salts. Ten litre fermentations were implemented to study the kinetics of substrate utilization and product formation. The pH at which the fermentation was controlled appeared to be the critical parameter for batch growth of mixed cultures of Trichoderma reesei Rut C30 and Aspergillus phoenicis.

Evaluation of the hydrolytic potential of a crude cellulase from mixed cultivation of Trichoderma reesei and Aspergillus phoenicis

Mixed cultivation of Trichoderma reesei Rut C30 and Aspergillus phoenicis produced a cellulase complex which showed enhanced activity against cellulose. Initial rates of glucose production were improved up to twofold over cellulase from Trichoderma alone. For the mixed culture cellulase, the pH optimum was found to be slightly different when measured on the basis of glucose production rate (4.5–4.75), than if measured on the basis of production of total reducing sugars (4.0–4.25). The initial rate of glucose and reducing sugar production increased with temperature over the range tested (40–60°C). Stability of individual enzyme component activities were tested at 50 and 60°C. β-Glucosidase (cellobiase or β- d-glucoside glucohydrolase, EC 3.2.1.21) activity was most labile at elevated temperatures ( t 1 2 = 10 h at 60°C and 48 h at 50°C). The mixed culture enzyme was more resistant to end product inhibition by glucose than the Trichoderma enzyme. Hydrolysis of steam exploded aspen wood (SEAW) by the mixed culture cellulase was markedly improved over that achieved by the Trichoderma cellulase.

Cellulase and beta-glucosidase production by mexied culture of trichoderma reesei rut C30 and aspergillus phoenicis

When lignocellulosic materials are hydrolysed using cellulase fromTrichodermareesei, cellobiose accumulates due to a deficiency in β-glucosidase activity of the enzyme complex. Cellobiose decreases the rate and extent of hydrolysis through feedback inhibition of exo β-1,4-glucanase. Cellulase produced through mixed culture ofTrichoderma andAspergillus showed increased β-glucosidase activity and greatly improved hydrolytic potential.