Renewable biosynthesis of isoprene from wastewater through a synthetic biology approach: the role of individual organic compounds

● Engineered E. coli can use wastewater as the only feedstock to product isoprene. ● Glucose, maltose, glycerol and lactate can be used for isoprene biosynthesis. ● Starch, protein and acetate can’t feed the E. coli growth. ● The optimum C/N ratio and essential nutrients addition enhance isoprene yield. ● The cost and CO2 emission are significantly reduced by using wastewater. The biosynthesis of isoprene offers a more sustainable alternative to fossil fuel-based approaches, yet its success has been largely limited to pure organic compounds and the cost remains a challenge. This study proposes a waste-to-wealth strategy for isoprene biosynthesis utilizing genetically engineered E. coli bacteria to convert organic waste from real food wastewater. The impact of organic compounds present in wastewater on E. coli growth and isoprene production was systematically investigated. The results demonstrated that with filtration pretreatment of wastewater, isoprene yield, and production achieved 115 mg/g COD and 7.1 mg/(L·h), respectively. Moreover, even without pretreatment, isoprene yield only decreased by ~ 24%, indicating promising scalability. Glucose, maltose, glycerol, and lactate are effective substrates for isoprene biosynthesis, whereas starch, protein, and acetate do not support E. coli growth. The optimum C/N ratio for isoprene production was found to be 8:1. Furthermore, augmenting essential nutrients in wastewater elevated the isoprene yield increased to 159 mg/g COD. The wastewater biosynthesis significantly reduced the cost (44%–53% decrease, p-value < 0.01) and CO2 emission (46%–55% decrease, p-value < 0.01) compared with both sugar fermentation and fossil fuel–based refining. This study introduced a more sustainable and economically viable approach to isoprene synthesis, offering an avenue for resource recovery from wastewater.