Enhanced butanol production by Clostridium acetobutylicum fermentation using thermo-responsive poly(N-isopropylacrylamide)-grafted PDMS sponge as adsorbent material

BACKGROUND: Butanol production through ABE (acetone, butanol, and ethanol) fermentation has attracted a great deal of attention because of its potential to replace petroleum-based fuels. Low butanol production and productivity due to butanol inhibition are the main challenges to make ABE fermentation viable economically. In this work, polydimethylsiloxane (PDMS) sponge and thermos-responsive poly(N-isopropylacrylamide)-grafted PDMS (PNIPAAm-PDMS) sponges (with different mass fractions of PNIPAAm on the PDMS surface) were investigated as adsorbents for butanol. RESULTS: The butanol model solutions showed that the adsorption–desorption efficiency of different types of sponges for butanol is highly temperature-dependent. Higher temperatures exhibited higher adsorption efficiency. In contrast, lower temperatures markedly increased the desorption efficiency for butanol. PNIPAAm-PDMS with 8.0 wt% of PNIPAAm on the PDMS surface showed as the best adsorbent for butanol. It had adsorption efficiency of 14, 24 and 46% at 25, 37 and 50 °C, respectively. Moreover, 96% of butanol adsorbed was recovered at 25 °C. When it was coupled with a batch ABE fermentation by Clostridium acetobutylicum, butanol production increased by 102% compared to batch fermentation without adsorption. A semi-continuous fermentation with the initial feeding time at the 60th hour exhibited as the optimum condition. However, it failed to enhance butanol productivity due to a high accumulation of butanol in the broth. Then, a semi-continuous fermentation with adsorption was conducted, yielding total butanol production of 20 g/L. CONCLUSION: PNIPAAm-PDMS sponge is proposed as an adsorbent to overcome butanol inhibition in ABE fermentation by temperature manipulation to recover butanol.