Integrated approach in the biotreatment of starch wastes by Rhizopus oligosporus: kinetic analysis Original Research Article

A biotreatment process of strach-contaminated wastes coming from potato manufacturing plants was studied and developed with an integrated approach. The reduction of strach content in the waste, and of the relative COD, is obtained in a mechanical stirred bioreactor under aerobic conditions, producing a suitable biomass potentially useful as additive in animal feeding. In this manner the COD reduction of the waste may be obtained with the production of a useful biomass with a market value. At the same time the microorganism produces glucoamylase, an extracellular enzyme, that may be recovered from the fermentation broth. The kinetics of microbial growth was monitored in synthetic media to evaluate the effect of starch concentration, pH, and stirring condition during the biotreatment process in shaken flasks and bioreactor tests. The biomass was recovered by filtration, washed by water and finally lyophilized. A kinetic model useful to describe the kinetics of microbial growth was developed: substrate consupmtion, microbial growth and enzyme production can be followed by the model. Considering the obtained experimental results the potential technical feasibility of the process was demonstrated.