Optimisation of Simultaneous Saccharification and Fermentation (SSF) for Biobutanol Production Using Pretreated Oil Palm Empty Fruit Bunch

Abstract

This study was conducted in order to optimise simultaneous saccharification and fermentation (SSF) for biobutanol production from a pretreated oil palm empty fruit bunch (OPEFB) by Clostridium acetobutylicum ATCC 824. Temperature, initial pH, cellulase loading and substrate concentration were screened using one factor at a time (OFAT) and further statistically optimised by central composite design (CCD) using the response surface methodology (RSM) approach. Approximately 2.47 g/L of biobutanol concentration and 0.10 g/g of biobutanol yield were obtained after being screened through OFAT with 29.55% increment (1.42 fold). The optimised conditions for SSF after CCD were: temperature of 35 °C, initial pH of 5.5, cellulase loading of 15 FPU/g-substrate and substrate concentration of 5% (w/v). This optimisation study resulted in 55.95% increment (2.14 fold) of biobutanol concentration equivalent to 3.97 g/L and biobutanol yield of 0.16 g/g. The model and optimisation design obtained from this study are important for further improvement of biobutanol production, especially in consolidated bioprocessing technology.

Improved Biobutanol Production in 2-L Simultaneous Saccharification and Fermentation with Delayed Yeast Extract Feeding and in-situ Recovery

“…The sugar should not be less than 40 g/L or else the cells will be triggered to produce more acids instead of solvents 19 . However, OPEFB loading of more than 5% will reduce the mixing efficiency and cause the inability of the cells to withstand at high substrate loading 17 . Therefore, this present study utilized 5% of OPEFB in the whole process after being optimised by Razali et al .…”

“…Therefore, this present study utilized 5% of OPEFB in the whole process after being optimised by Razali et al . 17 .

Figure 1Effect of different impellers, with and without baffle on the enzymatic saccharification of pretreated oil palm empty fruit bunch in a 2-L bioreactor.

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“…2. The main aim of conducting SHF in a 2-L bioreactor is to compare with SHF conducted in a 125-mL serum bottle 13,17 , as well as a control to be compared with the SSF process. In this study, approximately 30 g/L of the sugar from OPEFB was supplied in this fermentation because this is the highest sugar concentration that can be obtained from the saccharification of OPEFB, which was also reported by Ibrahim et al .…”

“…Then, 6 g/L of pre-sterilized yeast extract and 2 mL of each P2-medium components 13 were added into the solution and sparged with nitrogen gas for about 1 h until no oxygen was detected. The fermentation was initiated by inoculating 15% of prepared inoculum (OD 620 set at 1.0) into the bioreactor 17 . The inoculated media were incubated at 35 °C with an agitation speed of 150 rpm for 120 h. Two-ml of the liquid sample was withdrawn from the bioreactor and kept at −20 °C prior to sample analysis.…”

“…This SSF process was conducted based on the optimal conditions reported by Razali et al . 17 . SSF was conducted by adding 5% of pretreated OPEFB into a 2-L bioreactor and autoclaved at 121 °C for 15 min.…”