Production of extracellular laccase by the white-rot fungus Pycnoporus sanguineus was examined in batch submerged cultures in shake flasks, baffled shake flasks and a stirred tank bioreactor. The biomass growth in the various culture systems closely followed a logistic growth model. The production of laccase followed a Luedeking-Piret model. A modified Luedeking-Piret model incorporating logistic growth effectively described the consumption of glucose. Biomass productivity, enzyme productivity and substrate consumption were enhanced in baffled shake flasks relative to the cases for the conventional shake flasks. This was associated with improved oxygen transfer in the presence of the baffles. The best results were obtained in the stirred tank bioreactor. At 28 °C, pH 4.5, an agitation speed of 600 rpm and a dissolved oxygen concentration of ~25 % of air saturation, the laccase productivity in the bioreactor exceeded 19 U L(-1 )days(-1), or 1.5-fold better than the best case for the baffled shake flask. The final concentration of the enzyme was about 325 U L(-1).
This study examined the potential of untreated and alkali-pretreated sugarcane bagasse (SCB) in cellulase, reducing sugar (RS) and fungal biomass production via solid state fermentation (SSF) using Pycnoporus sanguineus. The impact of the composition, structure and cellulase adsorption ability of SCB on the production of cellulase, RS and fungal biomass was investigated. From the morphological and compositional analyses, untreated SCB has relatively more structural changes with a higher percentage of depolymerisation on the cellulose, hemicellulose and lignin content compared to alkali-pretreated SCB. Thus, untreated SCB favoured the production of cellulase and fungal biomass whereas alkali-pretreated SCB yielded a higher amount of RS. The composition and morphology of untreated SCB did not encourage RS production and this suggested that RS produced during SSF might be consumed in a faster rate by the more abundantly grown fungus. Besides that, alkali-pretreated SCB with higher cellulase adsorption ability could have adsorbed the cellulase produced and resulted in a lower cellulase titre. In short, the production of specific bioproducts via SSF is dependent on the structure and composition of the substrate applied.
Matched MeSH terms: Pycnoporus/growth & development