Modelling Mixed Microbial Culture Polyhydroxyalkanoate Accumulation Bioprocess towards Novel Methods for Polymer Production Using Dilute Volatile Fatty Acid Rich Feedstocks

Abstract

Volatile fatty acid (VFA) rich streams from fermentation of organic residuals and wastewater are suitable feedstocks for mixed microbial culture (MMC) Polyhydroxyalkanoate (PHA) production. However, many such streams have low total VFA concentration (1–10 gCOD/L). PHA accumulation requires a flow-through bioprocess if the VFAs are not concentrated. A flow through bioprocess must balance goals of productivity (highest possible influent flow rates) with goals of substrate utilization efficiency (lowest possible effluent VFA concentration). Towards these goals, dynamics of upshift and downshift respiration kinetics for laboratory and pilot scale MMCs were evaluated. Monod kinetics described a hysteresis between the upshift and downshift responses. Substrate concentrations necessary to stimulate a given substrate uptake rate were significantly higher than the concentrations necessary to sustain the attained substrate uptake rate. A benefit of this hysteresis was explored in Monte Carlo based PHA accumulation bioprocess numerical simulations. Simulations illustrated for a potential to establish continuous flow-through PHA production bioprocesses even at a low (1 gCOD/L) influent total VFA concentration. Process biomass recirculation into an engineered higher substrate concentration mixing zone, due to the constant influent substrate flow, enabled to drive the process to maximal possible PHA production rates without sacrificing substrate utilization efficiency.

A review on microbes mediated resource recovery and bioplastic (polyhydroxyalkanoates) production from wastewater

“…Microbial consortia or mixed microbial culture (MMC) offers an advantage over monoculture as it allows the exploitation of synergistic dynamics, diverse metabolic capabilities, and pathways to deal with high organic load or complex pollutants present in wastewater [ 126 ]. The interactions among microorganisms, including mutualism, competition, predation, and syntrophy, drive the functionality and resilience of mixed cultures in various environments [ 127 ].…”

“…MMC also offers higher stability and functionality that can withstand environmental fluctuations and changing conditions [ 126 ]. Advancements in omics technologies and computational modeling offer insights into the intricate networks and metabolic interactions within mixed microbial communities [ 132 ].…”

“…However, some waste has low concentrations of total VFAs i.e. 0.5 to 10 gL − 1 [ 126 ] while higher VFAs concentrations can be found in specific cases such as dairy [ 141 ] and fishing [ 142 ] industry residues, these may not provide a sufficiently large and widespread source for industrial-scale MMC PHA production. Colombo et al [ 143 ]., valorized organic acids from municipal waste and yielded PHA production of 223 ± 28 g.kg − 1 total OA fed .…”

Advances in Polyhydroxyalkanoate (PHA) Production, Volume 3

“…To reach this goal, dynamics of upshift and downshift respiration kinetics were evaluated for MMCs on laboratory and pilot scale. Despite a constant influent substrate flow, biomass recycling into a mixing zone, which was engineered to contain higher substrate concentration, allowed for running the process at optimum PHA productivity, without compromising substrate utilization efficiency [ 19 ].…”