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PubMed1979

Production of cellulases by Trichoderma reesei QM 9414 in fed-batch and continuous-flow culture with cell recycle.

The scope in improving enzyme productivities from the cellulose fermentation process is examined in laboratory-scale fermentors. The maximum productivity (30 IU/liter hr) is attained in a continuous-culture process with cell recycle using modified medium containing 0.5% cellulose. Optimum dilution rate and recycle ratio are determined as 0.025 hr-1 and 1.2, respectively, for the process. The system is analyzed and steady-state equations for predicting enzyme protein concentrations in the fermentor are developed. In fed-batch cultures, slow addition of cellulose at high concentrations can improve enzyme productivity by as much as 33% over a batch process. The scope and results of using modified medium for cellulase production are also presented.

Cellulase↗
PubMed1985

Production, localization and glucose repression of beta-glucosidase in Trichoderma longibrachiatum.

Optimal production of beta-glucosidase was obtained by incubating the culture at 27 degrees C in a growth medium that had an initial pH of 5.0 and contained cellobiose. The bulk of the enzyme (70%) was present in a cell-associated state (cell debris and cytosol) while only a small portion (30%) appeared in the culture filtrate. When cellulosic substrates were used, the major portion of the enzyme (70%) appeared in the extracellular fraction. A repression of the enzyme occurred in the presence of glucose. A drop of the pH of the medium during the exponential growth phase coincided with a rapid inactivation of the enzyme. The glucose effect was most likely mediated by adverse effects of low pH on the integrity of the enzyme.

Enzyme Repression↗
PubMed1993

Microbial degradation of aquatic biomass by Trichoderma viride 992 and Aspergillus wentii 669 with reference to the physical structure.

There was a considerable change in the structural parameters of both the lignocellulosic substrates. This change was confirmed by infrared (IR) spectroscopy and X-ray diffraction data, which revealed the presence of phenolic groups in the peaks range 1310-1410 and 1200 cm-1 with large crystalline substrates. These were found to be reduced after treatment with alkali. Enzyme/s activity were found to be increased after pretreatment of hydrolysed substrates. The structural modifications in both the substrates were further evidenced by the results obtained after enzymatic hydrolysis of alkali-treated substrates.

Aspergillus↗
PubMed1981

Kinetics of cellulase production in Trichoderma viride on microcrystalline cellulose.

During the cultivation of a wild strain of T. viride on microcrystalline cellulose the synthesis of cell-bound FP cellulases precedes cell growth. During the growth they are released into the medium as extracellular enzymes. The rete of synthesis of extracellular FP cellulases increases during cell growth, reaching a maximum at the beginning of transition to the stationary phase when the cell growth rate decreases. In contrast to extracellular enzymes, the rate of synthesis of bound cellulases during active growth is almost constant. In the stationary phase the rate of synthesis of both FP cellulases drops sharply, creasing well before cell lysis sets in and before the maximum level of extracellular cellulases is attained.

Cellulase↗
PubMed1985

Acquisition of small colonies of Trichoderma viride for genetic analysis.

Growth and mutual interlacing of colonies of T. viride is affected by concentration of nutrients and presence of inhibitors in the culture medium. The most convenient colony restrictors were Bengal red, Ox Gall and sodium deoxycholate while L-sorbose and 2-deoxy-D-arabino-hexose were less efficient.

Culture Media↗
PubMed2003

Nucleosome transactions on the Hypocrea jecorina (Trichoderma reesei) cellulase promoter cbh2 associated with cellulase induction.

The 5' regulatory region of the cbh2 gene of Hypocrea jecorina contains the cbh2 activating element (CAE) which is essential for induction of cbh2 gene expression by sophorose and cellulose. The CAE consists of two motifs, a CCAAT box on the template strand and a GTAATA box on the coding strand, which cooperate during induction. Northern analyses of cbh2 gene expression has revealed an absolute dependence on induction, but no direct effect of Cre1-mediated carbon catabolite repression. Investigation of the chromatin structure in the wild-type strain showed that, under repressing conditions, there is a nucleosome free region (nfr) around the CAE, which is flanked by strictly positioned nucleosomes. Induction results in a loss of positioning of nucleosomes -1 and -2 downstream of the CAE, thus making the TATA box accessible. Simultaneous mutation of both motifs of the CAE, or of the CCAAT-box alone, also leads to shifting of nucleosome -1, which normally covers the TATA-box under repressing conditions, whereas mutation of the GTAATA element results in a narrowing of the nfr, indicating that the proteins that bind to both motifs in the CAE interact with chromatin, although in different ways. A cellulase-negative mutant strain, which has previously been shown to be altered in protein binding to the CAE, still displayed the induction-specific changes in nucleosome structure, indicating that none of the proteins that directly interact with CAE are affected, and that nucleosome rearrangement and induction of cbh2 expression are uncoupled. Interestingly, the carbon catabolite repressor Cre1 is essential for strict nucleosome positioning in the 5' regulatory sequences of cbh2 under all of the conditions tested, and induction can occur in a promoter that lacks positioned nucleosomes. These data suggest that Cre1, the Hap2/3/5 complex and the GTAATA-binding protein are all involved in nucleosome assembly on the cbh2 promoter, and that the latter two respond to inducing conditions by repositioning nucleosome -1.

Base Sequence↗