Thermal behavior of native, washed and steam exploded lignocellulosic biomass samples

The aim of this study was to evaluate the chemical changes in the main components (cellulose, hemicellulose and lignin) of various lignocellulosic biomass samples during the steam explosion pretreatment. Pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) and thermogravimetry/mass spectrometry (TG/MS) measurements have been performed on different native, washed and steam exploded woody (willow and spruce) and herbaceous (hemp, wheat straw and sweet sorghum bagasse) biomass samples. The main differences between the thermal decomposition of the samples are interpreted in terms of the altered structure of the biomass samples by the effective steam explosion treatment and the different alkali ion contents which have been determined using inductively coupled plasma-optical emission spectroscopy (ICP-OES) method. In order to separate these two effects, the native biomass samples have been washed with hot water to remove the main parts of the potassium and sodium ions. The concentration of K+ and Na+ has been reduced in the treated biomass samples so the thermal decomposition mechanism has been altered due to the elimination of the catalytic effects. Principal Component Analysis (PCA) has been used to find statistical correlations between the data. The functional group compositions of the lignin molecules have been modified significantly as indicated by the pyrograms and the score plot of the PCA. The amount of hemicellulose has been reduced. On the other hand, the relative amount of the structurally modified cellulose has been increased in the samples by the steam explosion pretreatment step

Ethanol production from mixtures of wheat straw and wheat meal

Background: Bioethanol can be produced from sugar-rich, starch-rich (first generation; 1G) or lignocellulosic (second generation; 2G) raw materials. Integration of 2G ethanol with 1G could facilitate the introduction of the 2G technology. The capital cost per ton of fuel produced would be diminished and better utilization of the biomass can be achieved. It would, furthermore, decrease the energy demand of 2G ethanol production and also provide both 1G and 2G plants with heat and electricity. In the current study, steam-pretreated wheat straw (SPWS) was mixed with presaccharified wheat meal (PWM) and converted to ethanol in simultaneous saccharification and fermentation (SSF). Results: Both the ethanol concentration and the ethanol yield increased with increasing amounts of PWM in mixtures with SPWS. The maximum ethanol yield (99% of the theoretical yield, based on the available C6 sugars) was obtained with a mixture of SPWS containing 2.5% water-insoluble solids (WIS) and PWM containing 2.5% WIS, resulting in an ethanol concentration of 56.5 g/L. This yield was higher than those obtained with SSF of either SPWS (68%) or PWM alone (91%). Conclusions: Mixing wheat straw with wheat meal would be beneficial for both 1G and 2G ethanol production. However, increasing the proportion of WIS as wheat straw and the possibility of consuming the xylose fraction with a pentose-fermenting yeast should be further investigated

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

Fractionation of cellulase and beta-glucosidase in a Trichoderma reesei culture liquid by use of two-phase partitioning

An aqueous two-phase system based on the two polymers poly(ethylene glycol) and dextran has been used for the fractionation of cellulase enzymes present in culture liquid obtained by fermentation with Trichoderma reesei. The activities of beta-glucosidase and glucanases were separated to high degree by using the two-phase systems for a counter-current distribution process in nine transfer steps. While the glucanases had high affinity to the poly(ethylene glycol) rich top phase the beta-glucosidase was enriched in the dextran-containing bottom phase. Multiple counter-current distribution performed indicates the heterogeneity of beta-glucosidase activities assuming at least four isoenzyme forms. One step concentration of beta-glucosidase by using system with 46:1 phase volume ratio resulted in 16 times higher enzyme activity

Production of β-Glucosidase in Mixed Culture of Aspergillus niger BKMF 1305 and Trichoderma reesei RUT C30

The aim of the present study was to investigate a new approach to β-glucosidase production of an Aspergillus strain using cheap lignocellulosic material i.e. waste paper in order to substitute glucose, a generally used carbon source, and thereby reduce the production cost. The enzyme production was performed and optimized for the highest β-glucosidase yield in cofermentation with a Trichoderma strain to support the degradation of cellulose and to provide the non-cellulolytic Aspergillus with water soluble carbon source. Batch fermentation experiments of Aspergillus niger BKMF 1305 and Trichoderma reesei RUT C30 were carried out in shake flask cultures. The factors influencing the enzyme production, such as the concentrations of nutrients and carbon source, the inoculum ratio of the two species, and the delay in A. niger inoculation were investigated using a 23 full factorial design. The results were analyzed with the response surface methodology using commercially available software, Statistica for Windows. All three examined factors were found significant. The highest β-glucosidase activity of 3.07 IU/mL was obtained after 7 days of incubation, if 3.3 % Aspergillus and 6.7 % Trichoderma inoculum were added at the same time to modified Mandels’ medium, in which the concentration of nutrients was doubled compared to normal Mandels’ medium and the carbon source concentration was set to 20 g/L waste paper

Production of β-Glucosidase in Mixed Culture of Aspergillus niger BKMF 1305 and Trichoderma reesei RUT C30

The aim of the present study was to investigate a new approach to β-glucosidase production of an Aspergillus strain using cheap lignocellulosic material i.e. waste paper in order to substitute glucose, a generally used carbon source, and thereby reduce the production cost. The enzyme production was performed and optimized for the highest β-glucosidase yield in cofermentation with a Trichoderma strain to support the degradation of cellulose and to provide the non-cellulolytic Aspergillus with water soluble carbon source. Batch fermentation experiments of Aspergillus niger BKMF 1305 and Trichoderma reesei RUT C30 were carried out in shake flask cultures. The factors influencing the enzyme production, such as the concentrations of nutrients and carbon source, the inoculum ratio of the two species, and the delay in A. niger inoculation were investigated using a 23 full factorial design. The results were analyzed with the response surface methodology using commercially available software, Statistica for Windows. All three examined factors were found significant. The highest β-glucosidase activity of 3.07 IU/mL was obtained after 7 days of incubation, if 3.3 % Aspergillus and 6.7 % Trichoderma inoculum were added at the same time to modified Mandels’ medium, in which the concentration of nutrients was doubled compared to normal Mandels’ medium and the carbon source concentration was set to 20 g/L waste paper