In this study, the co-culture bacteria of Clostridium sporogenes and Enterobacter aerogenes were immobilized onto two different support materials: loofah sponge and activated carbon (AC) sponge. Both immobilized co-cultures were used in the batch fermentation of pineapple residues for biohydrogen production. The performance of both immobilized loofah and AC sponge was compared with free cell (FC) co-culture in terms of biohydrogen cumulative production and production rate within 48 hr fermentation time. It was found that the immobilized co-culture on AC sponge produced the highest rate of biohydrogen of 35.9 mmol/hr/Lsubstrate compared to loofah and FC co-culture after 24 hr fermentation. However, in terms of preservation of biohydrogen production rate, loofah as a support showed better consistency in terms of performance for 48 hr fermentation time compared to AC. This study also showed that the pH of substrate has a relation to the optical density (OD600) reduction of the bacteria, which could affect biohydrogen production rate.
Pineapple residues are one of potential biomass feedstock for biohydrogen production. The most convenient way to produce biohydrogen from pineapple residual is through fermentation proses. The process is environmentally friendly and consumes low energy, but generally the process has low yield production. Various strategies can be used to increase production, including the use of immobilized cells in fermentation. The performance of the process can be explained as realistically as possible by the appropriate kinetic model. In this work, a kinetic analysis on fermentative biohydrogen production using different hydrogenproducing bacteria immobilized onto activated carbon sponge has been performed. The performance of cumulative and biohydrogen production rate were assessed using modified Gompertz equation via Excel solver application. All fermentation processes were carried out at a condition of initial pH 7 and temperature of 32 ± 1°C, with 30% v/v inoculum of working volume in batch process. Three different hydrogen-producing bacteria were used, namely Escherichia coli, Enterobacter aerogenes and Clostridium sporogenes, were immobilized onto activated carbon sponge and in free cell form as comparison. Based on best fitting curve results on the cumulative biohydrogen production, it was found that modified Gompertz equation were fitted well with all the experimental results of all regression values, R2 were greater than 0.9. This study also presented that E. aerogenes and C. sporogenes able to produce better result compared to E.coli in term of production of biohydrogen The modified Gompertz equation would be useful for further analysis of biohydrogen production performance of selected hydrogen-producing bacteria culture immobilized onto activated sponge from pineapple residues.
Soil Microbial Fuel Cell (SMFC) is a device that using bacteria in soils as a biocatalyst. These bacteria, called exoelectrogenic bacteria are oxidizing organic substrates to release electrons, which then harvested in an external circuit to produce bioelectricity. Despite all the potential, the bioelectricity production from soils is still low and its relation with SMFC conditions is uncertain. Hence, the main objective in this study is to enhance and stabilize the bioelectricity production of SMFC by additional glucose, nutrient broth and Escherichia coli (E. coli) as exoelectrogenic bacteria. A number of factors of SMFC performance were first identified to be preliminary investigated, that is the type of electrode, water addition to soil and distance between anode to cathode. It has been established in this study to use SMFC with the configuration of 9.5 cm in diameter and 15 cm height of the plastic container, with the 12 cm distance between carbon felt of anode and cathode. The electricity produced was measured by using a multimeter in term of voltage reading (mV). From this study, the highest bioelectricity produced was obtained from SMFC using nutrient broth with a maximum voltage of 700 mV. It has found that the additional E. coli bacteria did not increase the bioelectricity production. The use of E. coli needed to be combined with nutrient broth in order to achieve high and stable bioelectricity. It can be suggested that the indigenous bacteria that exist in the soils possibly played the role in producing bioelectricity.
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