Biomass For Biofuel Production Research Articles

Lactoserum as a moistening medium and crude inducer for fungal cellulase and hemicellulase induction through solid-state fermentation of apple pomace

Abstract Objectives The potential of lactoserum as a crude inducer and moistening medium for fungal cellulase and hemicellulase induction was tested through solid-state fermentation. Methodology Solid-state fermentation was conducted in Erlenmeyer flasks and plastic trays using apple pomace (AP) as solid substrate by Aspergillus niger NRRL 567 and A. niger NRRL 2001. Results Solid-state tray fermentation resulted in cellulase activities (IU g−1 dry weight basis) of 383.7 ± 17.9, 425.3 ± 21.3, 336.1 ± 16.2 and 4868 ± 39.8, respectively for FPase (filter paper cellulase), CMCase (carboxymethyl cellulase), BGL (β-glucosidase) and xylanase using A. niger NRRL 567. Similarly, A. niger NRRL 2001 resulted in enzyme activities (IU g−1) of 401 ± 23.8, 544.7 ± 24.5, 285.4 ± 11.7 and 4580.7 ± 34.5, respectively for FPase, CMCase, BGL and xylanase. The enzyme loading of FPase 50 IU g−1 substrate in the hydrolysis of AP resulted in (g kg−1): 509.3 ± 22.9 total sugar (48 h), 109.3 ± 5.7 reducing sugar (48 h), 16.1 ± 0.8 glucose (60 h) and 10.4 ± 2.0 xylose, respectively whereas hydrolysis of BSG resulted in (g kg−1): 375.7 ± 16.2 total sugars (36 h), 114.6 ± 4.0 reducing sugar (60 h), 18.1 ± 0.9 glucose (60 h) and 19.8 ± 2.0 xylose (48 h), respectively. Conclusions This study demonstrated the potential of SSF as a simple and cheap technology for higher cellulase and hemicellulase production using negative cost AP waste which could eventually help to utilize abundant lignocellulosic biomass for production of biofuels and other value-added products.

Bm Lignin Structure and Chemical Compositional Characteristics of Switchgrass

Switchgrass contains high content of cellulose which is suitable to enzymetically hydrolyze to glucose, and is a good potential biomass for biofuel production. The paper studied a kind (Alamo, CA993,CA992,Kanlow) switchgrass ball milled lignin structure using 13C NMR and 31P NMR. Both NMR lignin spectrums showed little difference of this switchgrass. Its extractive-free compositional components were also analyzed like acid insoluble lignin, acid soluble lignin, ash and carbohydrates separately. Its acid insoluble and soluble lignin contents were close to each other in the range of 21% and 2.5% respectively. Their carbohydrates are made mainly up of glucose and xylose, which fractions are around 52% to 40% based on the whole carbohydrates.

Populus resequencing: towards genome-wide association studies

Genome-wide association studies (GWAS) have been used to identify regions of the genome related to various phenotypes in humans, corn, rice and cattle. Successful application of this approach to bioenergy crops such as Populus requires 1) an appropriate mapping population, 2) high-quality phenotypic data and 3) informative genotypic data. With the goal of reducing the recalcitrance of lignocellulosic biomass for economic production of biofuels and understanding basic mechanisms of cell wall formation in Populus we established 4 clonally replicated common gardens experiments each with 1100 native P. trichocarpa genotypes collected from along the northwest coast of the U.S. and Canada. A high-throughput phenotyping pipeline was developed to measure cell wall chemistry, pretreatment response and enzymatic sugar release. Initially 18 genotypes were resequenced to an average 30X depth in order to design a SNP array to test for statistical association using MMAX and PCA methods of testing among ca. 2500 candidate genes. Genetic structure and linkage disequilibrium (LD) was assessed using SSR and SNP markers. Outlying genotypes were excluded from the analyses and estimates of LD were used to design the bead array. Candidate genes were selected based on QTL intervals, expression profiling within developing xylem and expert opinion. MMAX and PCA results revealed similar significant associations for all measured phenotypes and several SNPs within the candidate gene set explain a relatively high degree of the phenotypic variance. As a result, resequencing has continued in order to conduct GWAS in Populus; the complete set of 1100 genotypes will be complete in 2012.

Small Angle Neutron Scattering Reveals pH-dependent Conformational Changes in Trichoderma reesei Cellobiohydrolase I: IMPLICATIONS FOR ENZYMATIC ACTIVITY

Cellobiohydrolase I (Cel7A) of the fungus Trichoderma reesei (now classified as an anamorph of Hypocrea jecorina) hydrolyzes crystalline cellulose to soluble sugars, making it of key interest for producing fermentable sugars from biomass for biofuel production. The activity of the enzyme is pH-dependent, with its highest activity occurring at pH 4-5. To probe the response of the solution structure of Cel7A to changes in pH, we measured small angle neutron scattering of it in a series of solutions having pH values of 7.0, 6.0, 5.3, and 4.2. As the pH decreases from 7.0 to 5.3, the enzyme structure remains well defined, possessing a spatial differentiation between the cellulose binding domain and the catalytic core that only changes subtly. At pH 4.2, the solution conformation of the enzyme changes to a structure that is intermediate between a properly folded enzyme and a denatured, unfolded state, yet the secondary structure of the enzyme is essentially unaltered. The results indicate that at the pH of optimal activity, the catalytic core of the enzyme adopts a structure in which the compact packing typical of a fully folded polypeptide chain is disrupted and suggest that the increased range of structures afforded by this disordered state plays an important role in the increased activity of Cel7A through conformational selection.

Optimizing microalgal biomass for biofuel production: the impact of glucose feeding on lipid and fatty acid profiles in Chlorella zofingiensis

Evaluation of: Liu J, Huang J, Sun Z et al. Differential lipid and fatty acid profiles of photoautotrophic and heterotrophic Chlorella zofingiensis: assessment of algal oils for biodiesel production. Bioresour. Technol. 102(1), 106–110 (2011) (In press).The production of environmentally friendly biofuels has become a major focus of scientists and politicians since the detrimental effects of fossil fuel combustion have become increasingly apparent. One of the established technologies today in this field is the production of biodiesel derived from plant lipids. The study of Jin Liu et al. investigated the differential lipid and fatty acid profiles of the microalga Chlorella zofingiensis in dependence of photoautotrophic or heterotrophic culturing conditions, respectively. The work showed that heterotrophic glucose feeding leads to far higher lipid yields and a strong increase of the relative amount of neutral lipids such as triacylglycerol. The fatty acid profile indicates that oil from heterotrophic C. zofingiensis cells should be of a similar quality as oil from crop plants. The authors conclude that heterotrophic culturing of C. zofingiensis could have a great potential for profitable biodiesel production in the future.

Brown rot fungal early stage decay mechanism as a biological pretreatment for softwood biomass in biofuel production

A current barrier to the large-scale production of lignocellulosic biofuels is the cost associated with the energy and chemical inputs required for feedstock pretreatment and hydrolysis. The use of controlled partial biological degradation to replace elements of the current pretreatment technologies would offer tangible energy and cost benefits to the whole biofuel process. It has been known for some time from studies of wood decay that, in the early stages of growth in wood, brown rot fungi utilise a mechanism that causes rapid and extensive depolymerisation of the carbohydrate polymers of the wood cell wall. The brown rot hyphae act as delivery vectors to the plant cell wall for what is thought to be a combination of a localised acid pretreatment and a hydroxyl radical based depolymerisation of the cell wall carbohydrate polymers. It is this quality that we have exploited in the present work to enhance the saccharification potential of softwood forest residues for biofuel production. Here we show that after restricted exposure of pine sapwood to brown rot fungi, glucose yields following enzymatic saccharification are significantly increased. Our results demonstrate the potential of using brown rot fungi as a biological pretreatment for biofuel production. © 2010 Elsevier Ltd.

Exploiting plant–microbe partnerships to improve biomass production and remediation

Although many plant-associated bacteria have beneficial effects on their host, their importance during plant growth and development is still underestimated. A better understanding of their plant growth-promoting mechanisms could be exploited for sustainable growth of food and feed crops, biomass for biofuel production and feedstocks for industrial processes. Such plant growth-promoting mechanisms might facilitate higher production of energy crops in a more sustainable manner, even on marginal land, and thus contribute to avoiding conflicts between food and energy production. Furthermore, because many bacteria show a natural capacity to cope with contaminants, they could be exploited to improve the efficiency of phytoremediation or to protect the food chain by reducing levels of agrochemicals in food crops.

Biomass Supply Chains for Biofuel Production – Contracting Issues

The advances in technology, government grants and socio-environmental issues have caused a shift from corn to cellulose as ethanol feedstock, with more than 25 cellulosic ethanol plants being constructed in various parts of US (Ethanol RFA, 2008). Such a change in production and investment climate has implications for locating these biorefineries, and integrated production with locally available feedstocks, chosen technologies, size and scope of operations. This study analyzes questions such as ‘why a cellulosic ethanol pilot plant technology was located in a particular region (site specificity)?’ and ‘what role does the feedstock type (input specificity) and its opportunity costs could play in selecting a location?’ A database of these pilot plants is being built to identify the density and variation of biomass distribution (e.g. annual vs. perennial; multiple farmers vs. single large feedstock supply cooperative) together with qualitative inputs from the feedstock suppliers in that region. This helps identify synergies between competing technologies (among enzymatic, thermochemical and combined bioprocessing technologies) and how biomass supply infrastructure would evolve in North America. The study links the characteristics of regional feedstock supply (e.g. farmers in case of Voyager Ethanol in Iowa or landfills in case of New Planet Energy in Florida) and how that is tied to the success of proposed cellulosic ethanol pilot plants. The importance of captive farming of biomass for biofuel production is examined (OBC, 2008). Preliminary evidence suggests that the bioenergy firm’s size is inversely related to vertically integrated production (through captive plantations, Altman, et al, 2007) i.e. the captive plantations can be expected to be beneficial only for the smaller sized biomass plants.

Designing the deconstruction of plant cell walls

Cell wall architecture plays a key role in the regulation of plant cell growth and differentiation into specific cell types. Gaining genetic control of the amount, composition, and structure of cell walls in different cell types will impact both the quantity and yield of fermentable sugars from biomass for biofuels production. The recalcitrance of plant biomass to degradation is a function of how polymers crosslink and aggregate within walls. Novel imaging technologies provide an opportunity to probe these higher order structures in their native state. If cell walls are to be efficiently deconstructed enzymatically to release fermentable sugars, then we require a detailed understanding of their structural organization in future bioenergy crops.