There are numerous organisms that rely on biomass degradation for their survival, often existing in the natural environment as a complex consortia of fungi, bacteria, and protozoa, working synergistically to decay the plant cell wall. All of these organisms are potential sources of enzyme discovery, but current commercial products for biomass treatment are derived from fungi because these organisms produce a complex mix of enzymes at high produc­tivity and catalytic efficiency, both of which are required for low-cost enzyme supply. Unlike most bacteria, which express complexes of many carbohydrate­degrading activities arrayed on molecular scaffolds physically attached to the bacterial cell wall, fungal cellulases are typically secreted into the growth medium, allowing cost-efficient separation of the active enzymes in a liquid form suitable for delivery to a hydrolysis reactor.

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