Calcium carbonate was evaluated as a replacement for the base during the fermentation of glycerol by a highly productive strain of 1,3-propanediol (PDO), viz., Clostridium butyricum JKT37. Due to its high specific growth rate (µmax=0.53h(-1)), 40g/L of glycerol was completely converted into 19.6g/L of PDO in merely 7h of batch fermentation, leaving only acetate and butyrate as the by-products. The accumulation of these volatile fatty acids was circumvented with the addition of calcium carbonate as the pH neutraliser before the fermentation was inoculated. An optimal amount of 15g/L of calcium carbonate was statistically determined from screening with various glycerol concentrations (20-120g/L). By substituting potassium hydroxide with calcium carbonate as the pH neutraliser for fermentation in a bioreactor, a similar yield (YPDO/glycerol=0.6mol/mol) with a constant pH was achieved at the end of the fermentation.
Biohydrogen production has received widespread attention from researchers in industry and academic fields. Response surface methodology (RSM) was applied to evaluate the effects of several key variables in anaerobic fermentation of glucose with Clostridium butyrium, and achieved the highest production rate and yield of hydrogen. Highest H2 yield of 2.02 mol H2/mol-glucose was achieved from 24 h bottle fermentation of glucose at 35 °C, while the composition of medium was (g/L): 15.66 glucose, 6.04 yeast extract, 4 tryptone, 3 K2HPO4, 3 KH2PO4, 0.05 L-cysteine, 0.05 MgSO4·7H2O, 0.1 MnSO4·H2O and 0.3 FeSO4·7H2O, which was very different from that for cell growth. Sugarcane bagasse and Jatropha hulls were selected as typical tropical biomass wastes to produce sugars via a two-step acid hydrolysis for hydrogen production. Under the optimized fermentation conditions, H2 yield (mol H2/mol-total reducing sugar) was 2.15 for glucose, 2.06 for bagasse hydrolysate and 1.95 for Jatropha hull hydrolysate in a 3L fermenter for 24 h at 35 °C, with H2 purity of 49.7-64.34%. The results provide useful information and basic data for practical use of tropical plant wastes to produce hydrogen.
Landfill leachate imposes a huge problem to the environment and human beings. This work focused on bioconversion of leachate to acetic and butyric acids by Clostridium butyricum NCIMB 7423. A continuous stirred tank reactor (CSTR) was applied and connected to fabricate membrane module. The leachate was collected from Pulau Burung Landfill Site (PBLS), Nibong Tebal, Penang. Prior to fermentation, leachate was treated to remove volatile fatty acid and adjusted to meet the minimum requirement of nutrients for anaerobic fermentation. Synthetic medium fermentation acts as a benchmark to the leachate fermentation. The outcomes indicated that the yield of acetic acid and butyric acid in synthetic medium fermentation was 0.70 g/L and 0.71 g/L, respectively. Meanwhile, leachate fermentation showed that the yield of acetic and butyric acid was 0.93 g/L and 1.86 g/L, respectively. High production of acetic and butyric acid showed that leachate fermentation is a green alternative to produce a cleaner product.
Acetone-butanol-ethanol (ABE) production from renewable resources has been widely reported. In this study, Clostridium butyricum EB6 was employed for ABE fermentation using fermentable sugar derived from treated oil palm empty fruit bunch (OPEFB). A higher amount of ABE (2.61 g/l) was produced in a fermentation using treated OPEFB as the substrate when compared to a glucose based medium that produced 0.24 g/l at pH 5.5. ABE production was increased to 3.47 g/l with a yield of 0.24 g/g at pH 6.0. The fermentation using limited nitrogen concentration of 3 g/l improved the ABE yield by 64%. The study showed that OPEFB has the potential to be applied for renewable ABE production by C. butyricum EB6.
In this study, an anaerobic mesophilic bacterial strain, namely Clostridium butyricum KBH1, was isolated from a natural source. This strain grew well and produced biogas with an average hydrogen concentration of 60% (v/v) in the Reinforced Clostridial Media (RCM). To study the basic nutrient requirements, three main nutrients namely peptone (Pep), yeast extracts (Yes) and glucose (Glu) were chosen as factors, using an experimental design. The experiments were run according to 23 Full Factorial Design, followed by the Response Surface Method (RSM). The fermentation was performed in 30 ml serum bottles with 20 ml working volume in a sterile and anaerobic condition at 37°C with 5% inoculums. The results from the Analysis of Variance (ANOVA) for the factorial design showed that all the three factors had significantly affected the gas production by the C. butyricum. The response surface plot of the gas production by C. butyricum showed that the gas production could be enhanced by increasing peptone and yeast extract concentrations up to 15 g/l and 24 g/l respectively, without showing any substrate inhibition. Meanwhile, the glucose concentration showed an optimum at the middle point (8 g/l) with possible substrate inhibition at a high concentration (12 g/l). The total biogas production could be correlated to the three factors, using the quadratic equation: Gas =0.17 + 7.11Glu - 0.02Pep + 0.77Yes - 0.53Glu2 + 0.09Glu*Pep. The experimental results showed that the strain could grow well in substrate with high organic nitrogen content such as POME and might be not suitable for substrate with high sugar content due to substrate inhibition.