Guar Gum Hydrogel Microbial Fuel Cell Using B.MEGATERIUM

Abstract

The main factors of a microbial fuel cell (MFC) are the anode and the microorganisms around it that produce electrons. This research focuses on increasing the efficiency of a MFC in plant-MFC (PMFC) or aquarium-like conditions by inoculating microorganisms that help produce electrons to the soil. Guar gum was used as a base structure as it can culture microorganisms and create a hydrogel by cross-linking with borax. [1,2] Bacillus megaterium was added to the hydrogel as it can survive under the basic conditions of borax while producing electrons. [3] Glucose was added as well to help culture the bacteria. Then, the change of voltage was observed along with the growth of B.megaterium. A compound consisting of 0.5% glucose, 1% Guar gum, 10% Borax, and B.megaterium culture medium was created with a volume ratio of 1:25:1:1 in each order. This compound will be named GGB-B. GGB-B was able to keep its shape as a hydrogel along with a voltage increase of 250mV compared to control due to the stable growth of B.megaterium. 100g of GGB-B was placed inside a beaker and was covered with aquarium soil. Two goldfishes (Carassius auratus) were added. Voltage, pH, and the health of goldfishes were observed for 9 days. The result was approximately a 150mV increase in voltage compared to control (tap water). pH decrease was about 1.3, showing a pH of 6.12. There was no change in the goldfishes, and the GGB-B under the aquarium soil fused with the soil as it disintegrated. Therefore, when electron-producing microorganisms such as B.megaterium are added to guar gum, the microorganisms would slowly spread over the soil, thereby increasing the efficiency of MFC. This could also apply to PMFC and aquarium-like conditions as well.