Co-production of ethanol and polyhydroxybutyrate from lignocellulosic biomass using an engineered Saccharomyces cerevisiae

The development of glucose/xylose co-fermenting Saccharomyces cerevisiae has improved bioethanol yield from lignocellulosic biomass, the most abundant and sustainable resource for net-zero production of fuels and chemicals. The co-production of value-added chemicals would further improve the economic feasibility of lignocellulosic bioethanol production. Here, we developed a glucose/xylose co-fermenting S. cerevisiae strain capable of co-producing polyhydroxybutyrate, a prominent biodegradable polymer, as an intracellularly accumulated co-product by introducing a polycistronic polyhydroxybutyrate biosynthetic pathway. The engineered strain accumulated polyhydroxybutyrate with a content of 64 mg/g DCW while maintaining extracellular production of ethanol with a high yield (0.43 g ethanol/g sugar). The co-production of ethanol and polyhydroxybutyrate was then evaluated using various types of biomass, including sugarcane bagasse, silver grass, and even cardboard boxes. This study demonstrates the feasibility of co-production of bioethanol and value-added chemicals to maximize the values derivable from lignocellulosic biomass.