Fernando Masarin

Chemical composition and enzymatic digestibility of sugarcane clones selected for varied lignin content.

BackgroundThe recalcitrance of lignocellulosic materials is a major limitation for their conversion into fermentable sugars. Lignin depletion in new cultivars or transgenic plants has been identified as a way to diminish this recalcitrance. In this study, we assessed the success of a sugarcane breeding program in selecting sugarcane plants with low lignin content, and report the chemical composition and agronomic characteristics of eleven experimental hybrids and two reference samples. The enzymatic digestion of untreated and chemically delignified samples was evaluated to advance the performance of the sugarcane residue (bagasse) in cellulosic-ethanol production processes.ResultsThe ranges for the percentages of glucan, hemicellulose, lignin, and extractive (based on oven-dry biomass) of the experimental hybrids and reference samples were 38% to 43%, 25% to 32%, 17% to 24%, and 1.6% to 7.5%, respectively. The samples with the smallest amounts of lignin did not produce the largest amounts of total polysaccharides. Instead, a variable increase in the mass of a number of components, including extractives, seemed to compensate for the reduction in lignin content. Hydroxycinnamic acids accounted for a significant part of the aromatic compounds in the samples, with p-coumaric acid predominating, whereas ferulic acid was present only in low amounts. Hydroxycinnamic acids with ester linkage to the hemicelluloses varied from 2.3% to 3.6%. The percentage of total hydroxycinnamic acids (including the fraction linked to lignin through ether linkages) varied from 5.0% to 9.2%, and correlated to some extent with the lignin content. These clones released up to 31% of glucose after 72 hours of digestion with commercial cellulases, whereas chemically delignified samples led to cellulose conversion values of more than 80%. However, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment.ConclusionSome of the experimental sugarcane hybrids did have the combined characteristics of high biomass and high sucrose production with low lignin content. Conversion of glucan to glucose by commercial cellulases was increased in the samples with low lignin content. Chemical delignification further increased the cellulose conversion to values of more than 80%. Thus, plants with lower lignin content required less delignification to reach higher efficiencies of cellulose conversion during the enzymatic treatment.

Laboratory and mill scale evaluation of biopulping of Eucalyptus grandis Hill ex Maiden with Phanerochaete chrysosporium RP-78 under non-aseptic conditions.

Abstract Biopulping of Eucalyptus grandis wood chips with Phanerochaete chrysosporium RP-78 was evaluated under non-aseptic conditions in laboratory and mill wood-yard. The ability of P. chrysosporium to compete with indigenous fungi present in fresh wood chips was notorious under controlled laboratory experiments. A subsequent step involved an industrial test performed with 10-ton of fresh wood chips inoculated and maintained at 37±3°C for 39 days in a biopulping pilot plant. Biotreated wood chips were pulped in a chemithermomechanical pulping mill. Net energy consumption during refining was 745 kWh ton-1 and 610 kWh ton-1 of processed pulp for control and biotreated wood chips, respectively. Accordingly, 18.5% net energy saving could be achieved. Biopulps contained lower shive content and had improved strength properties compared to control pulps. Tensile index improved from 25±1 N m g-1 to 33.6±0.5 N m g-1 and delamination strength from 217±19 kPa to 295±30 kPa.

Evaluation of Eucalyptus grandis Hill ex Maiden biopulping with Ceriporiopsis subvermispora under non-aseptic conditions

Abstract In biopulping, efficient wood colonization by a selected white-rot fungus depends on previous wood chip decontamination to avoid the growth of primary molds. Although simple to perform in the laboratory, in large-scale biopulping trials, complete wood decontamination is difficult to achieve. Furthermore, the use of fungal growth promoters such as corn steep liquor enhances the risk of culture contamination. This paper evaluates the ability of the biopulping fungus Ceriporiopsis subvermispora to compete with indigenous fungi in cultures of fresh or poorly decontaminated Eucalyptus grandis wood chips. While cultures containing autoclaved wood chips were completely free of contaminants, primary molds grew rapidly when non-autoclaved wood chips were used, resulting in heavily contaminated cultures, regardless of the C. subvermispora inoculum/wood ratio evaluated (5, 50 and 3000 mg mycelium kg−1 wood). Studies on benomyl-amended medium suggested that the fungi involved competed by consumption of the easily available nutrient sources, with C. subvermispora less successful than the contaminant fungi. The use of acid-washed wood chips decreased the level of such contaminant fungi, but production of manganese peroxidase and xylanases was also decreased under these conditions. Nevertheless, chemithermomechanical pulping of acid-washed samples biotreated under non-aseptic conditions gave similar fibrillation improvements compared to samples subjected to the standard biodegradation process using autoclaved wood chips.

Lignin chemistry and topochemistry during kraft delignification of Eucalyptus globulus genotypes with contrasting pulpwood characteristics

Abstract Eucalyptus globulus Labill. is a short-fibre resource for pulp and paper production. Ten different E. globulus genotypes with varied pulpwood quality and chemical composition were evaluated under kraft pulping conditions. Characterisation of the wood and pulp samples by thioacidolysis indicated that the content of syringyl units in β-O-4 linkages (S-β-O-4) was distinct for the studied genotypes. The highest S-β-O-4 levels were detected in the samples with the lowest original lignin and highest glucan levels. This group of samples provided the pulps with the lowest final lignin content at higher yields. UV microspectrophotometric (UMSP) evaluation of the wood chips revealed that the samples with the lowest lignin levels have the lowest UV absorbances at 278 nm (A278 nm) in the secondary walls (S2). During kraft pulping, lignin from the S2 was dissolved, whereas lignins from the middle lamella and cell corner lignin was not removed not even for prolonged reaction periods, independently of the evaluated genotype. The A278 nm values of the S2 were significantly lower in the pulps from the genotypes with less original lignin content.