TECHNOLOGY FOCUS - BIOTECHNOLOGY - Preferred Enzyme: The cathode enzyme or anode enzyme comprises more than one redox center, chosen from bilirubin oxidase, laccase, PQQ-dependent hydrogenase, lipoxygenase, superoxide dismutase and/or peroxidase. The cathode enzyme comprises bilirubin oxidase or superoxide dismutase. The anode enzyme comprises PQQ-dependent dehydrogenase or lipoxygenase.    TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Composition: The electron conductor comprises carbon-based material, metallic conductor, semiconductor, metal oxide or modified conductor, preferably carbon-based material chosen from carbon cloth, carbon paper, carbon screen printed electrode, carbon black, carbon powder, carbon fiber, single-walled carbon nanotube, double-walled carbon nanotube, multi-walled carbon nanotube, carbon nanotube arrays, diamond-coated conductors, glass carbon, mesoporous carbon, graphite, uncompressed graphite worms, delaminated purified flake graphite, high performance graphite, highly ordered pyrolytic graphite, pyrolytic graphite or polycrystalline graphite, preferably carbon nanotube. A biofuel cell using the bioanode or biocathode contains oxidant chosen from oxygen and peroxide, preferably oxygen.    TECHNOLOGY FOCUS - ORGANIC CHEMISTRY - Preferred Composition: The enzyme immobilization material is modified with hydrophobic cation larger than NH4+. The hydrophobic cation is ammonium-based cation, quaternary ammonium cation, alkyl trimethyl ammonium cation, organic cation, phosphonium cation, triphenyl phosphonium, pyridinium cation, imidazolium cation, hexadecylpyridinium, ethidium, viologen, methyl viologen, benzyl viologen, bis(triphenylphosphine) iminium, metal complex, bipyridyl metal complex, phenanthroline-based metal complex, (rubidium (bipyridine)3)2+ or (iron (phenanthroline)3)3+, preferably quaternary ammonium ion of formula: R4-N+(R1)(R3)R2.R1-R4 = H, optionally substituted hydrocarbyl or heterocyclo group, preferably H, methyl, ethyl, propyl, butyl, pentyl, hexyl, heptyl, octyl, nonyl or decyl, more preferably butyl.The fuel fluid is chosen from ammonia, methanol, ethanol, propanol, isobutanol, butanol, isopropanol, allyl alcohol, aryl alcohol, glycerol, propanediol, mannitol, glucuronate, aldehyde, carbohydrate, glucose, glucose-1 , D-glucose, L-glucose, glucose-6-phosphate, lactate, lactate-6-phosphate, D-lactate, L-lactate, fructose, galactose-1 , galactose, aldose, sorbose, mannose, glycerate, coenzyme A, acetyl coenzyme-A, malate, isocitrate, formaldehyde, acetaldehyde, acetate, citrate, L-gluconate, beta-hydroxysteroid, alpha-hydroxysteroid, lactaldehyde, testosterone, gluconate, fatty acid, lipid, phosphoglycerate, retinal, estradiol, cyclopentanol, hexadecanol, long-chain alcohol, coniferyl-alcohol, cinnamyl-alcohol, formate, long-chain aldehyde, pyruvate, butanal, acyl-coenzyme A, steroid, amino acid, flavin, NADH, NADH2, NADPH, NADPH2 or hydrogen, preferably methanol, ethanol or propanol, more preferably ethanol.    TECHNOLOGY FOCUS - POLYMERS - Preferred Composition: The enzyme immobilization material comprises micellar or inverted micellar structure, modified perfluoro sulfonic acid-polytetrafluoroethylene copolymer and hydrophobically modified alginate, hydrophobically modified polysaccharide. The polysaccharide is chitosan, cellulose, chitin, starch, amylase and/or alginate. The hydrophobically modified polysaccharide is of formula (1).n = integer;andR10,R11 = H, optionally substituted hydrocarbyl, preferably H, alkyl, hexyl or octyl.The hydrophobically modified polysaccharide has molecular weight of 90000-500000, preferably 225000-275000.