초록
<P><B>Abstract</B></P><P>Several studies have explored combining fermentative and purple bacteria to increase hydrogen yields from carbohydrates, but the metabolic interaction between these organisms is poorly understood. In an artificial co-culture containing <I>Clostridium cellulolyticum</I> and <I>Rhodopseudomonas palustris</I> with cellulose as the sole carbon source, we examined cell growth kinetics, cellulose consumption, H<SUB>2</SUB> production, and carbon transfer from <I>C. cellulolyticum</I> to <I>R. palustris</I>. When cultured alone, <I>C. cellulolyticum</I> degraded only 73% of the supplied cellulose. However, in co-culture <I>C. cellulolyticum</I> degraded 100% of the total cellulose added (5.5 g/L) and at twice the rate of <I>C. cellulolyticum</I> monocultures. Concurrently, the total H<SUB>2</SUB> production by the co-culture was 1.6-times higher than that by the <I>C. cellulolyticum</I> monoculture. Co-culturing also resulted in a 2-fold increase in the growth rate of <I>C. cellulolyticum</I> and a 2.6-fold increase in final cell density. The major metabolites present in the co-culture medium include lactate, acetate and ethanol, with acetate serving as the primary metabolite transferring carbon from <I>C. cellulolyticum</I> to <I>R. palustris</I>. Our results suggest that the stimulation of bacterial growth and cellulose consumption under the co-culture conditions is likely caused by <I>R. palustris'</I> removal of inhibitory metabolic byproducts (i.e., pyruvate) generated during cellulose metabolism by <I>C. cellulolyticum.</I></P> <P><B>Highlights</B></P><P>► The syntrophic metabolism of a bacterial co-culture was investigated. ► The total amount and rate of cellulose consumption were increased in co-cultures. ► The total amount and rate of hydrogen production were increased in co-cultures. ► Acetate was the major metabolite for carbon transfer in the co-culture. ► Pyruvate consumption boosted cellulose degradation in co-cultures.</P>