(i) Give the functions performed by each of the following
microbes :
(e) Aspergillus oryzae
Answers
Please Mark as brainlist
Explanation:
Characteristics of the Species
Aspergillus oryzae plays a pivotal role in Asian food manufacturing, such as saké, shoyu (soy sauce), and miso (soybean paste). For thousands of years, it has been used for making fermented food and beverages. In addition, A. oryzae has been used in the production of industrial enzymes for food processing. A. oryzae is accepted as a microorganism having generally regarded as safe status.
A. oryzae is an aerobic filamentous fungus and belongs to the Aspergillus subgenus Circumdati section Flavi, previously known as the A. flavus group. Aspergillus section Flavi contains industrially important species, such as A. oryzae, as well as agronomically and medically significant fungi, such as A. flavus and A. parasiticus, which produce a potent carcinogenic substance, aflatoxin. Taxonomically, A. oryzae is closely related to A. flavus, A. parasiticus, and A. sojae, which has also been used for shoyu fermentation for a long time. Despite such close relatedness, A. oryzae and A. sojae never produce aflatoxins and are used in fermented food manufacturing. Thus, it is of great importance to differentiate these four species accurately, although recent taxonomical studies on Aspergillus section Flavi have some controversial aspects.
A. oryzae is isolated from soils and plants, particularly rice. A. oryzae is named after its occurrence in nature and cultivation industrially on rice, Oryza sativa. A. oryzae has an optimal growth temperature of 32–36 °C (±1 °C) and is unable to grow above 44 °C. It has an optimal growth pH of 5–6 and can germinate at pH 2–8. It has been reported that A. oryzae could grow in corn flour with a water content of about 16%. It generally can grow on media with a water activity (aw) above 0.8, but it rarely grows below 0.8.
Like most other fungi, A. oryzae grows vegetatively as haploid multinucleate filaments, designated hyphae, or mycelia. Hyphae of A. oryzae extend at the apical tips and multiply by branching, so that the colony covers the surface of the solidified agar medium after several days of incubation. Hyphal growth keeps on going in liquid medium as long as the hyphae are not exposed to air atmosphere. Conidiophore structures, however, which bear asexual reproductive spores called conidia (Figure 1), are produced when hyphae are transferred onto solidified agar medium. When grown on the surface of an agar medium, the colony is initially white because of the vegetative hyphal growth, and then it turns to yellowish green as a large amount of conidia form. In most strains of A. oryzae, the color of fresh culture or conidia is yellowish green, but that of old culture is brown, sometimes green with brown shades. Conidial heads are usually globose to radiate, 100–200 μm in diameter. In A. oryzae, sexual life cycle has not been found as in other industrially important filamentous fungi, such as A. niger and Penicillium chrysogenum. Conidia of A. oryzae are haploid, but multinucleate (conidia have mostly two to four or more nuclei) in contrast to uninucleate conidia of A. nidulans or A. niger. This makes genetic manipulation of A. oryzae more difficult, compared with A. niger. Conidia are large, 5–8 μm in diameter, and spherical to slightly oval. Conidial walls are mostly smooth to finely roughened. Most strains of A. oryzae have only phialides on the vesicles (uniseriate sterigmata), but some contain metulae and phialides (biseriate sterigmata). Stipes of conidiophores are colorless and mostly roughened, to occasionally smooth and less roughened. They are long, in the range 1–5 mm.
Explanation:
Aspergillus oryzae is a fungus widely used in traditional Japanese fermentation industries, including soy sauce, sake, bean curd seasoning and vinegar production. Filamentous fungi generally have the ability to produce various and vast amounts of enzymes in a secretory manner.