Optimization of beta-carotene production by Rhodotorula glutinis using high hydrostatic pressure and response surface methodology.

Rhodotorula glutinis RG6 was treated by high hydrostatic pressure (HHP) of 300 MPa for 15 min for improving its ability of beta-carotene production. After the treatments of 5 repeated cycles, the mutant strain RG6p was obtained, beta-carotene production of which reached 10.01 mg/L, increased by 57.89% compared with 6.34 mg/L from parent strain RG6. To optimize the medium for beta-carotene fermentation by mutant RG6p, a response surface methodology (RSM) approach was used in conjunction with a factorial design and a central composite design, and the maximum yield of beta-carotene (13.43 mg/L), an increase of 34.17% compared to the control, was obtained at a pH 6.7 with an optimum medium (40 mL/250 mL) of yeast extract (4.23 g/L), glucose (12.11 g/L), inoculum (30 mL/L), tomato extract (2.5 mL/L), peanut oil (0.5 mL/L), and (NH(4))(2)SO(4) (5 g/L).

A Chinese fermented soybean food.

Sufu or furu is a fermented soybean product originating in China. It is a cheese-like product with a spreadable creamy consistency and a pronounced flavour. Sufu is a popular side dish consumed mainly with breakfast rice or steamed bread. It has a long history and written records date back to the Wei Dynasty (220-265 AD). Sufu is made by fungal solid state fermentation of tofu (soybean curd) followed by aging in brine containing salt and alcohol. The present review is based on scientific data published in Chinese and international sources. Several types of sufu can be distinguished, according to processing method or according to colour and flavour. Choice of processing can result in mould fermented sufu, naturally fermented sufu, bacterial fermented sufu, or enzymatically ripened sufu. Depending on the choice of dressing mixture, red, white or grey sufu may be obtained. The stages of the process are discussed and include the preparation of tofu, the preparation of pehtze, salting and ripening. Fungal starters include Actinomucor spp., Mucor spp. and Rhizopus spp. The chemical composition is discussed with particular reference to the proximate composition, the amino acid content and profile, as well as the volatile flavour components of various types of sufu.