(110a) Synthetic Biology and Metabolic Engineering of Clostridia for a Sustainable Future

Clostridia are obligate spore-forming anaerobes commonly found in a wide range of natural environments such as soil, sewage, marine sediments, animal intestine, and plants. Due to the widespread habitat, Clostridia can catabolize an enormous variety of organic materials including lignocellulosic biomass and CO₂ gas. Synthetic biology and metabolic engineering of Clostridia enable controllable manipulation of complex cellular metabolisms to produce valuable chemicals from renewable feedstocks in a rapid and efficient manner, helping reduce our reliance on the conventional petroleum-based chemical synthesis. In this talk, I will present synthetic biology and metabolic engineering of Clostridia for developing sustainable bioeconomy. Two industrially important Clostridia, Clostridium thermocellum and C. acetobutylicum, were engineered to develop novel bioprocesses. First, C. thermocellum metabolism was engineered for one-step production of volatile short-chain esters from lignocellulosic biomass at elevated temperatures (>55℃). A thermostable ester biosynthesis enzyme compatible with thermophilic microbes including C. thermocellum was developed by engineering promiscuity of chloramphenicol acetyltransferase. Push-and-pull metabolic engineering enhanced short-chain ester production from Avicel cellulose by >170-fold, developing a thermophilic CBP microbial platform for volatile short-chain ester production. Second, the Weizmann process was redesigned by engineering C. acetobutylicum for selective acetone production. Using a state-of-the-art CRISPR/Cas9 genome editing tool, the metabolism of C. acetobutylicum was successfully rewired to minimize ethanol and butanol formation and maximize acetone production. Finally, I will discuss challenges and opportunities of Clostridia for microbiome engineering.