Promising cellulolytic fungi isolates for rice straw degradation

The objective of this study was to evaluate the potential of eight fungal isolates obtained from soils in rice crops for straw degradation in situ. From the initial eight isolates, Pleurotus ostreatus T1.1 and Penicillium sp. HC1 were selected for further characterization based on qualitative cellulolytic enzyme production and capacity to use rice straw as a sole carbon source. Subsequently, cellulolytic, xylanolytic, and lignolytic (Pleurotus ostreatus) activity on carboxymethyl cellulose, oat xylan, and rice straw with different nitrogen sources was evaluated. From the results obtained it was concluded both isolates are capable to produce enzymes necessary for rice straw degradation. However, their production is dependent upon carbon and nitrogen source. Last, it was established that Pleurotus ostreatus T1.1 and Penicillium sp. HC1 capability to colonize and mineralize rice straw, in mono-and co-culture, without affecting nitrogen soil content.     

In vitro production of the biological control agent Heterorhabditis indica SL0708 in different agar media

ABSTRACT

Heterorhabditis indica SL0708 is an entomopathogenic nematode isolated from Valle del Cauca-Colombia, whose bacterial symbiont, Photorhabdus luminescens subsp. akhurstii SL0708, has potential to control pests of economic importance in Colombia. Since in vivo production does not supply its demand, this investigation evaluated H. indica SL0708 production on different agar media. Five culture media (I, II, III, IV and V) were evaluated for productivity and pathogenicity of infective juveniles (IJs). IJs emerged between 11 and 16 days after inoculation in all media, with a total of 2.7?×?10⁴ and 4.7?×?10⁶ IJs produced during 15 days after IJs emergence, with maximum productivity at day five and high variability. Pathogenicity to Galleria mellonella larvae was not significantly different between in vitro and in vivo produced IJs on all media tested. Media IV and V were selected for their higher productivity. Subsequently, nematode inoculum size was evaluated in selected media at 2000, 4000 and 6000?IJs ml^?1, but significant differences were not observed in productivity and pathogenicity. Lastly, lipid source influence was evaluated in medium IV comparing canola, olive and soy oils. None of the plant-based oils had a significant effect on IJs production and pathogenicity. A medium was selected for H. indica SL0708 IJs production which was suitable in terms of productivity, culture time and pathogenicity of IJs produced. The medium and parameters selected in this study could be applied as an alternative for mass production of this entomopathogenic nematodes.     

Degradation of Chrysanthemum (Dendranthema grandiflora) wastes by Pleurotus ostreatus for the production of reducing sugars

In Colombia, a great amount of waste is generated during the cut-off and harvest stages in flowers culture. This study examines the possibility of degrading Chrysanthemum wastes by using Pleurotus ostreatus, Trametes versicolor, and Phanerochaete chrysosporium cultures; this has not been studied previously. The initial effect of fungi on the degradation of Chrysanthemum wastes were studied individually and in co-cultures. The highest degradation was by P. ostreatus. After that, the influence of pH and waste, copper, and manganese concentrations on reducing sugars concentration were determined in a submerged culture in 100 mL Erlenmeyer flasks. There was a significant effect of manganese and waste concentrations on sugar concentration, while the effect of copper concentration and pH were not significant. Following, the process was carried out in a 1.5 L reactor at the optimal values of the variables studied in Erlenmeyer flask but varying air injection from 0 to 2 vvm. The highest concentration of sugars was 21.2 g/L with 78% of glucose content at 6.3% w/v of waste, 7.5 mM of Mn and Cu and 2 vvm of air injection. Finally, laccase, Manganese peroxidase, endo-1,4-β-glucanase, exo-1,4-β-glucanase and 1,4-β-glucosidase were detected in the extract obtained under these conditions. The highest activities were obtained for laccase (4,694 U/L) and 1,4-β-glucosidase (9,513 U/L).     

Ethanol production by Saccharomyces cerevisiae using lignocellulosic hydrolysate from Chrysanthemum waste degradation

Ethanol production derived from Saccharomyces cerevisiae fermentation of a hydrolysate from floriculture waste degradation was studied. The hydrolysate was produced from Chrysanthemum (Dendranthema grandiflora) waste degradation by Pleurotus ostreatus and characterized to determine the presence of compounds that may inhibit fermentation. The products of hydrolysis confirmed by HPLC were cellobiose, glucose, xylose and mannose. The hydrolysate was fermented by S. cerevisiae, and concentrations of biomass, ethanol, and glucose were determined as a function of time. Results were compared to YGC modified medium (yeast extract, glucose and chloramphenicol) fermentation. Ethanol yield was 0.45 g g^?1, 88 % of the maximal theoretical value. Crysanthemum waste hydrolysate was suitable for ethanol production, containing glucose and mannose with adequate nutrients for S. cerevisiae fermentation and low fermentation inhibitor levels.