Production of 2-phenylethanol by microbial mixed cultures allows resource recovery of cane molasses wastewater.

Abstract

Given resource depletion and environmental protection, the resource utilization of wastewater has attracted intensive attentions. In this study, cane molasses wastewater was used to produce 2-phenylethanol (2-PE) that is an important raw material in the fragrance industry. Repeated batch cultivations were conducted to screen and adapt the microbial- mixed culture for 2-PE production. The microbial-mixed culture endured 6 g/L 2-PE with a highest biomass of 1.7 g/L. The optimized parameters (35 °C, pH 7.0 and 0.8 vvm air flow-rate) in batch culture obtained the highest 2-PE production of 988 mg/L. Subsequently, the continuous 2-PE production was carried out in an internal airlift loop bioreactor. A highest 837.5 mg/L 2-PE production with a yield of 8.4 mg/g-COD was achieved at hydraulic retention time of 4 days. The main metabolic byproducts included acetate, lactate and ethanol. Finally, the community composition was analyzed using denaturing gradient gel electrophoresis. The dominant microorganisms were identified to be Bacillus sp., Pseudomonas sp., Candida tropicalis, Aspergillus niger, Saccharomyces cerevisiae, Kluyveromyces hubeiensis, Rhodotorula glutinis and Pichia kudriazevi. This work proposes that mixed culture biotechnology is suitable to continuously produce 2-PE from wastewater.