Effect of Buffering System on Acetone-Butanol-Ethanol Fermentation by Clostridium acetobutylicum ATCC 824 using Pretreated Oil Palm Empty Fruit Bunch

Abstract

Change of pH has been identified as the most significant parameter in modulating the transition between the conversions of acids into solvents in acetone-butanol-ethanol (ABE) fermentation by Clostridia. Thus, ABE fermentation at various phosphate buffer concentrations and initial pH values was conducted using pure glucose and sugars derived from pretreated oil palm empty fruit bunch (OPEFB). A higher solvent concentration (2.93 g/L) was obtained in the fermentation using 20 g/L of glucose with buffer compared with one without buffer that produced 1.34 g/L of solvents. Approximately 8.77 and 9.15 g/L of solvents were produced from fermentation using 40 g/L of glucose with and without buffer, respectively. In the latter conditions, at an initial pH of 5.5, 8.77 g/L of solvents was obtained, which was the highest concentration compared to other initial pH values. Increasing the buffer concentration to 0.2 M at an initial pH of 6.0 resulted in acid accumulation of 16.83 g/L but reduced the solvent production to 1.36 g/L. In addition, ABE fermentation using 20 g/L of sugars from pretreated OPEFB produced 2.25 g/L of solvents with a yield of 0.13 g/g, which was comparable with fermentation using 20 g/L of glucose conducted in a buffering system.

Effect of Residual Extractable Lignin on Acetone-Butanol-Ethanol Production in SHF and SSF Processes

“…Cells produced more butanol (3.92 g/L) and less butyric acid (2.00 g/L) from OPLP-W than that from OPLP-UW (2.08 g/L butanol and 2.63 g/L butyric acid) at 60 h. This indicated that initial sugar concentration significantly affected the solvent and acid production, cells appear to produce more acids and fewer solvents when the initial sugar concentration is low. A similar observation has been reported previously, where only 2.93 g/L of solvents were produced from 20 g/L of glucose as compared to 8.77 g/L of solvents from 40 g/L of glucose [41].…”

Effect of Residual Extractable Lignin on Acetone-Butanol-Ethanol Production in SHF and SSF Processes

“…This indicated that initial sugar concentration significantly affected the solvent and acid production, cells appear to produce more acids and fewer solvents when the initial sugar concentration is low. A similar observation has been reported previously, where only 2.93 g/L of solvents were produced from 20 g/L of glucose as compared to 8.77 g/L of solvents from 40 g/L of glucose [31].…”

Simultaneous saccharification and fermentation of sago hampas into biobutanol by Clostridium acetobutylicum ATCC 824

“…In SHF using hydrolysate, the cells need to adapt with different kind sugar composition which limits the cells to re‐assimilate the acids to be converted into solvents. It should be noted that the amount of acid might be different intra‐ and extracellular as has been reported by Maddox et al and Ibrahim et al …”

“…The determination of starch content was done using iodine starch colorimetric methods reported by Nakamura, while the determination of lignocellulosic content was conducted based on the gravimetric method described by Goering and Van Soest . The ABE and organic acids were analysed using gas chromatography (Model GC‐17A, Shimadzu, Japan) equipped with column BP21 and flame ionization detector following the methods by Ibrahim et al . The sugar monomers were quantified using a HPLC (Jasco, Japan) equipped with a refractive index (RI) detector and a column (Shodex KS‐801, Japan) for ligand exchange chromatography.…”