Food fermentations are ancient technologies that harness microorganisms and their enzymes to improve the human diet. Fermented foods keep better, have enhanced flavours, textures and aromas, and may also possess certain health benefits including superior digestibility. For Buddhists and other vegetarians, fermented foods serve as palatable, protein-rich meat substitutes.
Suggested reading: Probiotics PublicationsAsian cuisines rely on a large repertoire of fermented foods. In particular,
Aspergillus oryzae and
A. sojae, sometimes called koji moulds, are employed in many ways. Their hydrolytic enzymes suit them for growth on starch and other carbohydrate-rich substrates. In the koji process, fungal enzymes perform the same function as the malting enzymes used in the beer fermentations of western cultures. The koji moulds release amylases that break down rice starch which in turn can be fermented to make rice wine. Fermented rice beverages have numerous local variations and names depending on country and region. Rice wine is called
shaoshing in parts of China,
sake in Japan,
takj or
yakju in Korea, as well as by many other names across Asia.
The koji moulds are also effective in a variety of legume fermentations of which miso and soy sauce are best known. Miso is a mixture of soybeans and cereals usually used to flavour soups. Soy sauce is a flavourful, salty liquid sauce made from soybeans that have been fermented by koji moulds, yeasts, as well as several halophilic bacteria. Other names for soy sauce include jiangyou (China),
makjang and
kaniang (Korea),
toyo (Philippines) and
siiu (Thailand).
Suggested reading: Probiotics PublicationsThe first patent on a purified microbial enzyme was awarded in 1894. Companies were established in New Jersey and New York to produce bulk enzymes from
Aspergillus and other microbes. Modern commercial enzymology is a thriving bio-based business in which
A. niger and
A. oryzae are among the major producers for hydrolytic enzymes. As high capacity secretors, their extracellular enzymes easily can be exploited for the production of enzymes used in the baking, beverage and brewing industries; in making animals feeds; and in the paper pulping industry.
A. niger has been developed as an efficient host for the production of heterologous proteins using genetic engineering techniques.
A. oryzae also has been extensively engineered.
New and more extensive uses for fungal enzymes are envisioned in contemporary biotechnology because experts on energy policy are focusing on 'green' methods of biomass transformation. Plant-derived biomass theoretically could replace petrochemical feedstocks for certain chemical processes. Moulds have numerous enzymes that can turn complex polymers into sugars, lipids and other simpler molecules that can be used for fuels and chemical synthesis. Although much of the research has focused on the genus
Trichoderma,
Aspergillus represents a huge potential for finding new enzymes that could be used to convert plant biomass into fuels and other industrially useful products.
Adapted from
An Overview of the Genus Aspergillus by
Joan W. Bennett writing in
Aspergillus: Molecular Biology and GenomicsFurther readingLabels: fermented food, Kaniang, Koji, Makjang, Rice wine, Sake, Shaoshing, Siiu, Takj, Toyo, Yakju