Electricity generation from carboxymethyl cellulose biomass: A new application of enzymatic biofuel cells

Exploitation of naturally abundant biomass to produce electricity has been a hot topic. This study demonstrates for the first time a new application of enzymatic biofuel cells (BFCs) for direct production of electricity from carboxymethyl cellulose (CMC) biomass. As one of the most important cellulose derivates, CMC can be easily obtained from cellulose and has a good solubility in water. To produce electricity from CMC, cellulase was used as the biocatalyst in solution to catalyze the hydrolysis of CMC into glucose and glucose was then used as the biomass to produce electricity through biofuel cell technology. The bioanode for the oxidation of glucose produced for cellulase-catalyzed CMC hydrolysis was constructed with glucose dehydrogenase (GDH) as the biocatalyst and with methylene green (MG) adsorbed onto single-walled carbon nanotubes (SWNTs) as the electrocatalyst for the oxidation of NADH. The biocathode for the reduction of oxygen was fabricated by crosslinking laccase onto SWNTs. To catalyze CMC hydrolysis into glucose, 0.5 mg/mL cellulase was added into 1 wt.% CMC solution in 0.10 M acetate buffer (pH 5.5) and the mixture was then allowed to stand for 1 h to give CMC hydrolyzed solution. Under these conditions, CMC was hydrolyzed into glucose and glucose was oxidized under the biocatalysis of GDH, as characterized with UV-vis spectroscopy. In the CMC hydrolyzed solution containing NAD+ cofactor, both the bioanode and biocathode exhibit a good bioelectrocatalytic activity toward the oxidation of glucose and the reduction of oxygen, respectively. With the presence of 10 mM NAD+ into the CMC hydrolyzed solution, the assembled BFC has an open circuit voltage of 0.75 V and a maximum power output of 128 μW cm−2 at 0.35 V under ambient air and room temperature. These values are comparable to or even higher than those with other techniques employed to produce electricity from cellulose or cellulose derivates. This study essentially opens a new application of biofuel cell technology for energy production from naturally abundant biomass.