Chapter 25 - Process Design and Optimization for Platform Chemical Biorefinery

Abstract

Platform chemicals are value-added compounds, which are also intermediates formed in the biosynthetic pathway of an organism during its metabolism. The biorefinery concept integrates the process that involves pretreated biomass for bioconversion to obtain biofuels along with other chemical compounds of commercial interest. A few of the platform chemicals, like furfural, levulinic acid, and succinate, were found to be starting materials for the production of hydrocarbon either by physical or thermochemical methods, and this methodology is economically well suited to produce fossil fuel equivalents. Although these compounds were considered as inhibitors of fermentation, they are necessary for the fuel economy to meet the growing energy demand. This chapter elaborates on the development of an elite strain to obtain higher productivity, reactor design, scaling up, product recovery, and downstream processing of various platform chemicals. Various factors that control reactor operations, like temperature, pH, O2 uptake rate, dissolved oxygen concentration, CO2 evolution rate, agitation, and their interplay between each other decides the titer of intermediate metabolites. The optimal production of platform chemicals is solely dependent on an engineered organism, which in turn improves the productivity of platform chemicals. Knowledge about the metabolic bottleneck governing the accumulation of desired products in the broth will enable a suitable physiological condition to be maintained inside the reactor. Therefore the development of an appropriate bioconversion methodology becomes important to maintain a uniform quality of product. This chapter addresses key developments in the microbial production of C3 platform chemicals, like propionic acid, 1,3-propanediol, and 3-hydroxypropionic acid, from various feedstocks. Various metabolic engineering strategies to enhance the channeling of major carbon flux to metabolize into C3 platform chemicals by the microbial route are also elaborated.