Cellulase enzyme production by various fungal strains on different carbon sources

In the process of making ethanol from lignocellulosics, enzyme production is still the most crucial and costly step. Trichoderma reesei Rut C-30 is the best known cellulase producer. This fungus is very good in endo- and exoglucanase production, however, the amount of β-glucosidase excreted is not sufficient for hydrolysis. In addition, T. reesei Rut C-30 is sensitive to inhibitors generated during steam-pretreatment of wood. In the present study, two good cellulase producers were selected from 16 fungal strains and investigated regarding filter paper activity (FPU) and β-glucosidase activity using inexpensive lignocellulosic carbon sources for cultivation. T. reesei Rut C-30 proved to be a good cellulase producer, resulting in a maximum FPU of 1.39 FPU ml Ś1 on washed, steam-pretreated willow, but the β-glucosidase activity was insufficient. High β-glucosidase activities were reached with T. viride OKI B1 on all substrates, with a maximum activity of 1.62 IU ml Ś1 on steam-pretreated spruce

Β-glucosidase production of two different Aspergillus strains

Β-glucosidase has an important role in cellulose degradation by cleaving the cellobiose to glucose units. Supplementation of Trichodermacellulase with exogenous β-glucosidase is needed to prevent the inhibition effect of cellobiose on exoglucanases and endoglucanases.Production of β-glucosidase by Aspergillus niger and Aspergillus phoenicishas been investigated under different fermentations. Both strains were appropriate for enzyme production at high level under the applied conditions. Cultivation of A. phoenicison Mandels' medium containing a complex nitrogen source has resulted in a higher β-glucosidase activity than on Vogel's medium. In an air-lift fermenter A. phoenicis grew in the shape of beads with 1.41 IU g–1 cell-associated enzyme activity. The fungal pellets can be used as in situ immobilized enzyme preparation. A. niger produced extracellular β-glucosidase at the level of 2.1 IU ml–1 in stirred-tank fermenter with a yield of 210 IU g–1 glucose and productivity of 21.8 IU l–1 h–1

Evaluation of an online fermentation monitoring system

The need to introduce promising bioethanol production technologies calls for advanced laboratory techniques to study experiment designs and to obtain their results in a quick and reliable way. Real time monitoring based on general principles of ethanol fermentation, such as effluent CO2 volume, avoids time consuming steps, long lasting analyses and delivers information about the process directly. A device based on the above features and capable for real time monitoring on parallel channels was developed by the authors and is described in this paper. Both for calibration and for fermentation, test runs were carried out on different days and channels. Statistical evaluation was based on the obtained data. According to the t-test (P=0.05) and Grubbs analysis, the calibration method is reliable regardless of the date of calibration. When evaluating the fermentation results by ANCOVA acceptable standard derivations were obtained as impact of channel (58.8 ml), date (82.1 ml) and incorporating all impacts (116.2 ml). The final ethanol concentrations calculated based on the gas volume were compared to ones determined by HPLC and an average difference of 10% was found. Thus, the device proved to be advantageous in monitoring fermentation

Integrated Process of Arabinose Biopurification and Xylitol Fermentation Based on the Diverse Action of Candida boidinii

Hemicellulosic hydrolysates of agro-residues are promising raw materials for xylitol and arabinose production through biotechnological methods. Two-step acidic fractionation of corn fibre was developed to produce a glucose- and arabinose-rich hydrolysate and a xylose-rich hydrolysate. An integrated process of arabinose biopurification on the glucose- and arabinose-rich hydrolysate and xylitol fermentation on the xylose-rich hydrolysate using Candida boidinii NCAIM Y.01308 was introduced, in which cell mass produced in arabinose biopurification was used as inoculum in the xylitol fermentation. Aerobic biopurification resulted in an arabinose solution containing 9.2 g L–1 of arabinose with a purity of 90 %, based on total sugars. Xylitol fermentation under microaerobic conditions resulted in a xylitol yield of 53 % of theoretical and a xylitol concentration of 10.4 g L–1 in three days. Hence, an integrated biorefinery process of hemicellulosic hydrolysates was developed based on the diverse action of C. boidinii to purify arabinose and produce xylitol

Refining Hemp Hurds into Fermentable Sugars or Ethanol

Steam pretreatment is one of the most efficient pretreatment technologies employed prior to enzymatic hydrolysis of lignocellulosics to obtain high polysaccharide conversion. In this study, steam pretreatment of non-impregnated hemp hurds was investigated at two reactor scales (2 and 10 L) by varying the temperature from 200–230 °C. Glucan recoveries were relatively high (> 82 % of original content), while xylan recoveries ranged from 18–66 % of original. Conversions of glucan and xylan in enzymatic hydrolysis varied between X = 62–83 % and 46–96 %, respectively, based on glucan and xylan contents of the substrate. Ethanol yields in simultaneous saccharification and fermentation ranged from Y = 38–70 %, based on glucan and mannan contents of the substrate. The highest overall glucose yield was 336 g kg–1 dry hurds obtained at 210 °C, whereas the maximum sugar yield (glucose + xylose), 414 g kg–1 dry hurds, was achieved at 200 °C. The highest ethanol yield, 141 g kg–1 dry hurds, was obtained at 210 °C

Relevance of the light signaling machinery for cellulase expression in trichoderma reesei (hypocrea jecorina)

<p>Abstract</p> <p>Background</p> <p>In nature, light is one of the most important environmental cues that fungi perceive and interpret. It is known not only to influence growth and conidiation, but also cellulase gene expression. We therefore studied the relevance of the main components of the light perception machinery of <it>Trichoderma reesei </it>(<it>Hypocrea jecorina</it>), ENV1, BLR1 and BLR2, for production of plant cell wall degrading enzymes in fermentations aimed at efficient biosynthesis of enzyme mixtures for biofuel production.</p> <p>Findings</p> <p>Our results indicate that despite cultivation in mostly dark conditions, all three components show an influence on cellulase expression. While we found the performance of the enzyme mixture secreted by a deletion mutant in <it>env1 </it>to be enhanced, the higher cellulolytic activity observed for <it>Δblr2 </it>is mainly due to an increased secretion capacity of this strain. <it>Δblr1 </it>showed enhanced biomass accumulation, but due to its obviously lower secretion capacity still was the least efficient strain in this study.</p> <p>Conclusions</p> <p>We conclude that with respect to regulation of plant cell wall degrading enzymes, the blue light regulator proteins are unlikely to act as a complex. Their regulatory influence on cellulase biosynthesis involves an alteration of protein secretion, which may be due to adjustment of transcription or posttranscriptional regulation of upstream factors. In contrast, the regulatory function of ENV1 seems to involve adjustment of enzyme proportions to environmental conditions.</p