ABSTRACT
Aerobic microorganisms can generally produce lignocellulose-degrading enzymes more rapidly and in larger amounts than anaerobic microorganisms. This aerobic property can be utilized to quicken the hydrolysis of solids to their soluble constituents such as carbohydrates, amino acids, and volatile acids, which can subsequently be converted to biogas in an anaerobic digester. Aerobic pretreatment should ideally be limited to a very short duration; otherwise, significant amount of organic substrates that would have been converted to biogas may be lost to carbon dioxide. Enzymatic pretreatment has been successfully used in anaerobic treatment of wastes from dairies, brewery, distilleries, and abattoirs. Alkali pretreatment is more commonly used than acid pretreatment due to its compatibility with anaerobic digestion process since it increases the alkalinity of the substrate and consequently able to cancel out low pH resulting from the acidogenesis. Chemical pretreatment can be combined with thermal and enzymatic treatment.
