No abstract

Cultivation of specialty mushrooms on lignocellulosic wastes represents one of the most economical organic recycling processes. Compared with other cultivated mushrooms, very little is known about the nature of the lignocellulolytic enzymes produced by the edible and medicinal fungus Grifola frondosa, the parameters affecting their production, and enzyme activity profiles during different stages of the developmental cycle. In this work we investigated the enzymes that enable G. frondosa, to colonize and deconstruct two formulations based on industrial lignocellulosic by-products. G. frondosa degraded both substrates (oak-sawdust plus corn bran, and oak/corn bran supplemented with coffee spent-ground) decreasing 67 and 50% of their lignin content, along with 44 and 37% of the polysaccharides (hemicellulose and cellulose) respectively. 35.3% biological efficiency was obtained when using oak sawdust plus corn bran as substrate. Coffee spent-ground addition inhibited mushroom production, decreased growth, xylanase and cellulase activities. However, taking into account that G. frondosa successfully colonized this residue; this substrate formula might be considered for its growth and medicinal polysaccharide production. Although G. frondosa tested positive for Azure B plate degradation, a qualitative assay for lignin-peroxidase, attempts to detect this activity during solid state fermentation were unsuccessful. Enzyme activities peaked during colonization but declined drastically during fruiting body formation. Highest activities achieved were: endoglucanase 12.3, exoglucanase 16.2, β-glucosidase 2.3, endoxylanase 20.3, amylase 0.26, laccase 14.8 and Mn-peroxidase 7.4 U/g dry substrate.

Three species of white rot-fungi (Pleurotus ostreatus, Coriolus versicolor, and Lentinula edodes) were grown on 12 solid media based on several lignocellulosic materials (oak sawdust, coconut husks, coffee husks and corn bran) during 49 days. The media had varied carbon/nitrogen ratios and CuSO 4 content. The objective of the work was to evaluate the effect of the media formulation on the production of lignocellulolytic enzymes and degradation of lignocellulosic components by the three fungal species. C. versicolor exhibited the highest ability to degrade the three main polymers of the lignocellulosic waste materials employed and to produce ligninases with titers as high as 107 U/g solid substrate in the case of laccase. In addition, a mathematical model describing the fermentation kinetics of the cell biomass growth, degradation of lignocellulosic components, and lignocellulolytic enzyme production for the fungal species/medium combination exhibiting the best performance under solid-state fermentation conditions was proposed and validated in the case of C. versicolor. The mathematical model could be used to provide valuable information on the process itself as well as to contribute to the development of a future commercial process for lignocellulolytic enzyme production.

No abstract

Research Highlights: For the first time, a model was developed and applied for polysaccharide production from Trametes versicolor grown in agro-industrial and woody residues under solid-state fermentation (SSF) conditions. Background and Objectives: Fungal biomass is an important biological resource for biotechnological applications. Basidiomycetes fungi can be grown and developed on lignocellulosic materials such as forestry, wood, and agro-industrial residues in order to produce value-added products like bioactive polysaccharides. The objectives of this study were to evaluate the effects of the C/N ratio and copper concentration on biomass and polysaccharide production during solid state fermentation (SSF), as well as on the consumption of cellulose and hemicellulose, and lignin degradation, and to propose and validate a mathematical model to describe the overall SSF process. Materials and Methods: This research was carried out by growing three Basidiomycetes species (T. versicolor, Lentinula edodes, and Pleurotus ostreatus) on twelve formulations of solid substrates using mixtures of different inexpensive lignocellulosic residues such as oak sawdust, coconut fiber (hairs), coffee husks, and corn bran plus soybean oil, calcium carbonate, and two levels of copper(II) sulfate. Results: The three fungal species grew well on all substrate formulations. The statistical analysis of experimental data showed no significant effects on polysaccharide production, in the range of C/N and copper concentrations evaluated. Taking into account that the best polysaccharide production was obtained with T. versicolor (96.09 mg/g solid substrate), a mathematical model was proposed for this fungus to describe the behavior of the fermentation system from the obtained data of all the resulting combinations to reach the highest polysaccharide production by the fungus. Conclusions: The mathematical model disclosed in this work enabled to describe the growth and development of a higher basidiomycete under solid-state fermentation conditions on lignocellulosic substrates as well as the production of value-added products like polysaccharides with medicinal properties.