Temperature is an underestimated parameter to regulate the start-up of enhanced carbon chain elongation

Abstract

Temperature is an important environmental factor for optimized bioreactions. In this study, seven temperatures between 25 and 55 °C were undertaken to explore the product spectrums of carbon chain elongation in a mixed culture. Temperature was manifested to significantly affect the production rate, productivity, and selectivity of carbon chain elongation. 40 °C resulted in the highest caproate concentration (138.94 mmol-C/L) and the highest caproate selectivity up to 84.5 %. Combining microbial quantitative and diversity analysis, it was identified that the optimized temperature was owing to the competitive abilities of metabolically different species. The dominant bio-elongation Clostridium kluyveri preferred 35–45 °C. The competitive fermentative bacteria Clostridium magnum and Clostridium butyricum for acetate and butyrate anabolism preferred 25–35 °C, therefore, excluding lower temperature bio-elongation because of more acetate and butyrate conversion but not caproate. Metabolically diverse Pseudomonas sp was abundant at higher temperatures (50–55 °C) and longer duration, therefore, excluding thermophilic bio-elongation because of reduced caproate productivity.