초록
<P><B>Abstract</B></P> <P>The major challenge faced during acidogenic fermentation is the specificity in production of an individual biochemical in the fermentation broth. The production of biochemicals with special focus on propionic acid (H<SUB>Pr</SUB>) during acidogenic fermentation experiment was studied using cobalt (Co) and zinc (Zn) divalent ions as co-factors individually and synergistically in eleven different systems (RC<SUB>1</SUB>, RC<SUB>2</SUB>, R<SUB>1</SUB>-R<SUB>7</SUB>, R<SUB>Co</SUB> and R<SUB>Zn</SUB>). Further, to check the feasibility of H<SUB>Pr</SUB> production at higher scale, the two scale up systems (R<SUB>SU1</SUB> and R<SUB>SU2</SUB>) were operated with the best observed condition. Life cycle assessment (LCA) was also performed using the results pertaining to the best scale up bioreactor (R<SUB>SU2</SUB>). Supplementation of Co<SUP>2+</SUP> and Zn<SUP>2+</SUP> synergistically enhanced the H<SUB>Pr</SUB> fraction among other acids in the acidogenic fermentation at their respective optimum concentrations. Biosystem R<SUB>2</SUB> and its respective scale up reactor (R<SUB>SU2</SUB>) with Co<SUP>2+</SUP>/Zn<SUP>2+</SUP> concentration of 0.10/0.16 mM depicted highest H<SUB>Pr</SUB> concentration of 1.03 ± 0.05 g/L and 1.22 ± 0.06 g/L, respectively. Although control operated without Co<SUP>2+</SUP>/Zn<SUP>2+</SUP> supplementation showed higher total volatile fatty acid (VFA) (3.02 ± 0.15 g/L) production, H<SUB>Pr</SUB> fraction was observed to be lower in the system. The presence of peaks identified on voltammetric signature corresponding to redox mediator fumarate reductase (+0.030 V) and hydrogenase (2H<SUP>+</SUP>/H<SUB>2</SUB>) (+0.421 V) supported higher titres of H<SUB>Pr</SUB> in R<SUB>1</SUB> (Co<SUP>2+</SUP>/Zn<SUP>2+</SUP>: 0.01/0.06 mM) and R<SUB>2</SUB>. Life cycle assessment (LCA) carried out on the performance of H<SUB>Pr</SUB> production (R<SUB>SU2</SUB>) depicted process sustainability with lesser environmental impacts. The results further supported that Co<SUP>2+</SUP>/Zn<SUP>2+</SUP> synergistically can drive selective acidogenic fermentation towards H<SUB>Pr</SUB> production.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Optimum concentration of Co<SUP>2+</SUP> and Zn<SUP>2+</SUP> enhanced propionic acid fraction significantly. </LI> <LI> Absence of Co<SUP>2+</SUP> and Zn<SUP>2+</SUP> lead to higher butyric acid concentration in control system. </LI> <LI> Redox mediators presence co-related well with the end product. </LI> <LI> The study lead to sustainable production of propionic acid from wastewater. </LI> </UL> </P>