Fungal Cell Factories

One of the oldest methods, solid-state fermentation or the koji process, uses solid substrates, such as steam sterilized fibers or wheat bran, to cultivate the mold inoculum. This technique has been central to traditional food and beverage fermentations throughout Asia for thousands of years. Today solid-state fermentation is the cultivation method of choice for the commercial production of many enzymes and is gaining popularity in areas including bioremediation, detoxification of agro-industrial waste and biotransformation of crop residues for nutritional enrichment (Pandey et al., 2000 Singhania et al., 2009). 

Surface fermentation, used in the early production of both penicillin and citric acid, is carried out in shallow, nutrient medium-filled stainless steel trays instead of on a solid matrix. These trays are stacked within an aseptic fermentation chamber, and the fungal mycelium develops as a mat on the surface of the Uquid. 

Food and Industrial Bioproducts and Bioprocessing, First Edition. Edited by Nurhan Turgut Dunford. 2012 John Wiley Sons, Inc. Published 2012 by John Wiley Sons, Inc. 

In addition to optimizing fermentation parameters, fungal strain improvement and selection, either by classical mutagenesis or more sophisticated targeted molecular genetic approaches, are important research avenues to increase productivity and yield of industrial fermentations (Ruijter et al, 2002). 

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There are several examples describing the production of multiple compounds from biomass, or its derived components (Table 9.2). Dairy manure is a type of biomass that contains 12% hemicellulose, 22% cellulose, and 18% crude protein, representing a lai e potential source of carbohydrates as a carbon source and proteins as a nitrc en source. This substrate is uniquely adaptable and advant eous for animal manure refineries. The Rhizopus oryzae ATCC 20344 cell factory produced fumaric acid and chitin fiom the dairy manure. A liquid/ solid separation was used to obtain a nitrc en-rich liquid stream for fungal growth and subsequent chitin accumulation, while the manure s solid stream, which primarily consisted of carbohydrates in the form of cellulose and hemicellulose, could be converted by various pretreatment methods into monosaccharides for fumaric acid production. 

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