초록
<P><B>Abstract</B></P> <P>Conventional microbial protein production relies on the usage of pure chemicals and gases. Natural gas, which is a fossil resource, is the common input gas for bacterial protein production. Alternative sources for gas feedstock and nutrients can sufficiently decrease the operational cost and environmental impact of microbial protein production processes. In the present study, the effluents streams of municipal biowaste anaerobic digestion, were used to grow methane oxidising bacteria which can be used as protein source. Results demonstrated that a 40:60 CH<SUB>4</SUB>:O<SUB>2</SUB> (v/v) gas feeding resulted in microbial biomass production of 0.95 g-DM/L by a <I>Methylophilus</I> dominated community. When raw biogas was used as input for methane corresponding to the same initial methane partial pressure as before, instead of pure methane, the growth was partially hindered (0.61 g-DM/L) due to the presence of H<SUB>2</SUB>S (IC<SUB>50</SUB>: 1376 ppm). Hence, desulfurization is suggested before using biogas for microbial protein production. At semi-continuous mode, results showed that the produced biomass had relatively high protein content (>40% of dry weight) and the essential amino acids lysine, valine, leucine and histidine were detected at high levels.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The effluent of a biogas reactor was used to grow microbial protein. </LI> <LI> More than 0.95 g-DM/L were produced by a <I>Methylophilus</I> dominated community. </LI> <LI> Microbial growth was hindered by the presence of H<SUB>2</SUB>S (IC<SUB>50</SUB>: 1376 ppm) in raw biogas. </LI> <LI> The protein content was more than 41% and all essential amino acids were detected. </LI> </UL> </P>