Electricity generation from disaccharides using microbial fuel cells

Abstract

Researches on the finding renewable energy alternatives to fossil fuels have been great attention in recent years. The production of fuel and energy from lignocellulosic biomass such as agricultural residues and woody biomass has drawn significant attention because of the abundance, ready availability and renewable nature of these resources. The main components of lignocellulosic biomass are cellulose, hemicelluloses and lignin. Our previous study indeed demonstrated that all monosaccharides that can be directly generated from hydrolysis of lignocellulosic biomass were good sources for electricity generation in MFCs. However, lignocellulosic biomass cannot be directly utilized by microorganisms in MFCs for electricity generation. In other words, lignocellulosic material has to be converted to sugars or other low-molecular-weight compounds. The most commonly used method of converting lignocellulosic biomass to the sugars is through a diluteacid pre-treatment and subsequent acid- or enzymatic hydrolysis processes. The dilute-acid pretreatment and the subsequent acid hydrolysis generate a number of byproducts, such as furan derivatives, phenolic compounds and carboxylic acids Our previous study shows that most of the phenolic compunds and furan derivatives do not have inhbitory effect on electricity generation. However, upto know, there is no information about the electricity generation in air-cathode single chamber mediator-less microbial fuel cells from tested disaccharides. The acid hydrolysates from lignocellulosic materials such as pine wood or corn stover supposedly contain severall monosaccharides and disaccaharides previously described. Our preliminary results show that sulfuric acid hydrolysation (10%) of pine wood flour generate electricity in MFCs. However, it is poorly understood whether all the disaccharides can be utilized by bacteria in an MFC for electricity generation. Microbial fuel cell (MFC) technology uses microorganisms to catalyze the direct production of electricity from organic materials, and provides a new method for green energy generation from biomass. Various organic materials, such as glucose, xylose, acetate, butyrate, lactate, etc. as well as those from waste streams such as wastewaters can be used to generate direct electicity by MFCs. In this study, the direct production of electricity from disaccharides of lignocellulosic biomass was examined MFC performances by the disaccharides were evaluated as the following parameters: (1) Voltage generation, (2) power density generation, (3) Coulobic efficiency, (4) the removal of chemical oxygen demand and the effect of substrate concentration on electricity generation. Voltage was measured using a multimeter with a data acquisition system. Power density (mW $m^{-2}$) was calculated according to P=IV/A, where I is the current, V voltage, and A the projected area of the anode. Electricity was produced from all disaccharides tested, including D-maltose and D-cellobiose. The mixed bacterial culture enriched using sodium acetate as a carbon source adapted well to all carbon sources tested. The adaptation time, which was defined as the time between adding a disaccharide solution to a MFC and reaching a maximum power output at 1000 Ω, was similar for each disaccharide. However, once the bacteria adapted to a new disaccharide, electricity was quickly recovered when the disaccharide solution was refilled. Maximum power density obtained from these disaccharides were 1262±5 mW m-2 for D-cellobiose, 1893±67 mW $m^{-2}$ for D-maltose at current density of 0.44 and 0.66 mA $cm^{-2}$, respectively. For two disaccharides tested, the maximum voltage output at 120 Ω external resistance initially increased with the disaccharide concentration; however, further increases above a certain level did not improve the electricity generation Coulombic efficiency was 18% for D-cellobiose and 30% for D-maltose. For disaccharides tested, the relationship between the maximum voltage output and the substrate concentration appeared to follow saturation kinetics at 120 Ω external resistance. The estimated maximum voltage output ranged between 0.34-0.40 V and half-saturation kinetic constants of 626 to 733 mg $L^1$for D-cellobiose and D-maltose, respectively. Chemical oxygen demand (COD) removal was over 81 % for disaccharides tested. Results from this study indicated that lignocellulosic biomass-derived disaccharides might be a suitable resource for electricity generation using MFC technology.

Özet

Bu çalışmada, lignoselülozik biyokütlelerin asit hidrolizatlarında yaygın olarak bulunan disakkaritlerden elektrik üretimi, tek odalı, hava-katot mikrobiyal yakıt hücreleri kullanılarak araştırılmıştır. Başlıca iki disakkariti (D-sellobiyoz, D-maltoz) kapsayan karbon kaynakları ile elektrik üretimi gözlenmiştir. Sodyum asetat ile zenginleştirilmiş karışık bakteri kültürü, test edilen bütün disakkaritlere kolayca adapte olmuştur. Yeni karbon kaynağına adaptasyon için gerekli süre de benzerlik gösterdi. Test edilen disakkaritler için elde edilen en yüksek güç yoğunluğu, 0.44-0.66 mA $cm^{-2}$ direnç yoğunluğunda, sellobiyoz için 1262±5 mW $m^{-2}$, maltoz içinse 1893±67 mW $m^{-2}$ olarak bulunmuştur. Kolombik yeterlik sellobiyoz için yüzde 18, maltoz içinse yüzde 30 olarak bulunmuştur. Test edilen disakkaritler için, en yüksek volt eldesi ve substrat konsantrasyonu arasındaki ilişki 120 ohm dış dirençte doygunluk kinetiği sonuçları ile uyumluluk göstermiştir. Ön görülen en yüksek volt üretimi substratın çeşidine bağlı olarak, sellobiyoz için 0.34 V, yarı doygunluk kinetik sabiti, 626 mg $L^-$ ($R^2$= 0.971), maltoz için ise 0.40 V ve yarı doygunluk kinetik sabiti 733 mg $L^{-1}$ ($R^2$= 0.998) olarak bulunmuştur. Test edilen disakkaritler için yüzde 81’nin üzerinde kimyasal oksijen talebinde azalma sağlanmıştır. Test edilen disakkaritlerin elektrik üretiminde karbon kaynağı olarak kullanılabileceği keşfedilmiştir. Çalışmamızın sonuçları, lignoselülozik maddelerden türevli disakkaritlerin ve lignoselüloz türevli maddelerin ön muamele ile mikrobiyal yakıt hücreleri için uygun birer karbon kaynağı olabileceklerini göstermiştir.