An integrated bioprocess for fermentative production of protopanaxadiol by recycling ethanol waste during down-stream extraction process

Abstract: Solvent recovery and reutilization in bioprocess have great potential to reduce production cost and environmental harm. However, solvent recovery process is often energy-intensive and costly. In this study, we developed an integrated bioprocess for fermentative production of protopanaxadiol (PPD) from ethanol waste recycled in down-stream extraction process, achieving solvent recovery and reutilization in a cost-effective manner. In this integrated process, PPD isolation and purification were achieved by foam separation and resin chromatography, respectively; ethanol solution used as PPD extractant and chromatography eluent was recycled to be reused directly as yeast carbon source for PPD biosynthesis. Notably, in 3 batches of 5 L-fermentation productions, the recycled ethanol could compensate 81.3% of the ethanol used in fermentation. Since the lost PPD during chromatography elution was returned into the next-batch fermentation together with the recycled ethanol, the overall yield of 3-batch production (85.78%) was higher than the yield of single batch production (∼75%). This study demonstrates a promising integrated bioprocess for triterpene compounds production from ethanol waste.