Capability of Immobilized Clostridium beijerinckii TISTR 1461 on Lotus Stalk Pieces to Produce Butanol from Sugarcane Molasses

Immobilized Clostridium beijerinckii TISTR 1461 was used to enhance the butanol production efficiency from sugarcane molasses. Lotus stalk (LS) pieces were used as carriers for cell immobilization. Sugarcane molasses containing 50 g/L of sugar supplemented with 1 g/L of yeast extract was found to be an appropriate medium for bacterial cell immobilization on the LS pieces. Carrier size (4, 12 and 20 mm in length) and carrier loading (1:15, 1:30 and 1:45, w/v) were optimized for high levels of butanol production using response surface methodology (RSM). The batch fermentation was carried out under anaerobic conditions in 1 L screw-capped bottles at 37 degrees C and an agitation rate of 150 rpm. It was found that the optimum conditions for the butanol production were the carrier size of 4 mm and carrier loading of 1:31 (w/v). Under these conditions, the butanol concentration (P-B) was 12.89 g/L, corresponding to the butanol productivity (Q(B)) of 0.36 g/L.h and butanol yield (Y-B/S) of 0.36 g/g. These values were higher than those using free cells (P-B, 10.20 g/L, Q(B), 0.28 g/L.h and Y-B/S, 0.32 g/g). In addition, it was found that a 24 h incubation time for cell immobilization was appropriate for the immobilization process, which was confirmed by the results of the scanning electron microscope (SEM) and atomic force microscopy (AFM) images and specific surface area measurement. When the fermentation using the immobilized cells was carried out in a stirred-tank reactor (STR), column reactor (CR) and CR coupled with STR, the results showed that all reactors could be used to produce butanol production from the immobilized cells on LS pieces. However, the P-B using CR and CR coupled with STR were only 75% and 45% of those using the screw-capped bottle and STR.

Automated summary

The study focused on enhancing butanol production from sugarcane molasses using immobilized Clostridium beijerinckii, with Lotus stalk pieces as carriers. Optimization of carrier size and loading led to higher butanol production levels, with the optimal conditions being a carrier size of 4 mm and a loading ratio of 1:31 (w/v). Fermentation results showed improved butanol concentration, productivity and yield compared to using free cells, with a 24-hour immobilization time found to be appropriate. Fermentation in different types of reactors showed varying butanol production efficiencies, with screw-capped bottles and stirred-tank reactors (STR) achieving the highest levels.