Bioconversion of Waste Organic Matter into a Microbial Biomass Protein

Abstract

Food processing industries produce large quantities of wastewater with a high organic content. It is expensive to treat and dispose of this wastewater and it is a waste of organic resources. These waste streams can be converted from an economic liability to a source of revenue in the production of a high quality single cell protein. Several studies have been carried out on the production of microbial biomass protein from food processing wastewater using aerobic yeast cultures. The main challenge seems to be prevention of bacterial infection and maintaining the selected cultures in a full-scale continuous flow reactor. The hypothesis behind this research is that there is a range of operating conditions (e.g., SRT, pH, temperature) at which selected microorganism cultures have a competitive advantage and can be maintained in the system by a natural selection process. The concept was demonstrated with wastewater from the production of furfural, but the proposed methodology can be applied to any organic contaminants and microorganisms cultures. The results of this study indicated that furfural production wastewater can be effectively treated by aerobic yeast cultures to produce high quality microbial biomass. A COD removal efficiency of 92-95% and complete furfural degradation was achieved in a single stage process. A new approach for the design of biological processes aimed at the production of microbial biomass protein was proposed. The proposed approach is based on maintaining the selected microorganisms cultures in the system using natural selection processes. A methodology to define the range of operating conditions that prevent bacterial growth was proposed and verified in continuous flow experiments. Effluent soluble COD was significantly higher than the effluent biodegradable COD predicted possibly due to formation of SMP associated with substrate biodegradation.

The application of aerobic yeast for treatment of high strength food processing wastewater containing furfural

“…Bacterial competition within the yeast bioreactor was found to be a problem during continuous yeast production. The maximum specific growth rates, |x max , of C. utilis and bacteria were 0,13 h" 1 and 0.03 h" 1 and the value of half-saturation coefficient for substrate, K s , were 160 mg COD/L and 12 mg COD/L respectively at a pH 4.5 (Eliosov et al, 2002).…”

“…Many advantages of using yeast in wastewater treatment include their ability to cope with high strength organic matter from food processing industries, the direct decomposition of oils, their ability to deal with high organic and suspended solids loading, sludge generation reduction, good settling and dewatering properties, low oxygen requirements, and production of yeast cells as protein and vitamin source . Eliosov et al (2002) stated that yeast and other fungi are suitable microorganisms for conversion of waste organic matter into single cell protein. By selling these proteins as animal feed, it can compensate for the high cost of wastewater treatment.…”