This study aims to maximize the yield of gamma-linolenic acid (GLA) by a filamentous fungus, Mucor racemosus, using fermentation Douchi. Optimized fermentation conditions includes inoculum size and temperature. GLA content in Douchi by M. racemosus greatly varied in terms of fermentation temperature, from zero to 3.38% in total fatty acids, which means apart from fermentation temperature some other factors must affect GLA content in Douchi. The optimal amount of inoculums was 5.30 × 10 7 spores/10 g cooked soybean. The optimal temperature for fermentation was about 26℃. Under the optimal fermentation conditions, the GLA production of M. racemosus could be enhanced by optimizing the Douchi fermentation condition. Douchi, which contains GLA, may be directly absorbed through diet. Thus, Douchi may be a good kind of healthy food for people.Keywords: function food, douchi, gamma-linolenic acid, fermentation, Mucor racemosus *To whom correspondence should be addressed. E-mail: lhluhe@163.com Introduction Gamma-linolenic acid (GLA C18: 3Δ 6,9,12 ) is one of the important Polyunsaturated fatty acid in the human body with many medicinal and healthy effects, which is a precursor of prostaglandins and is also essential for patients who suffer from diabetes, cancer, aging, and infection (Gill and Valivety, 1997). This fatty acid is rarely found in common food, and the commercial sources are currently some seed oil plants, such as evening primrose and borage. (Kapoor and Huang, 2006;De et al., 2004;Sakuradani et al., 2009). However, several drawbacks have been reported in the plant sources (Gill and Valivety, 1997). Therefore, considerable interest has been focused on microorganisms, which enable accumulation of GLA-rich oils in their biomass (Zhang, 2002;Jangbua et al., 2009). Some genera of oleaginous filamentous fungi, mainly Mucor, Mortierella, Pythium have been reported as good PUFA producers. (Zhang, 2002). However, the production of microbial oils is so far not cost-competitive to the plant sources due to the significant problems of low productivity, insecurity and expensive downstream processing (Philips and Huang, 1996). It is known that some species of Mucor sp. can be used to ferment Douchi, one kind among many traditional Chinese foods consisting of fermented soybeans. It has played very important roles in Chinese diet for centuries. According to the distinct fermenting microorganism, Chinese douchi can be divided into three types: bacteria type (Shandong area), Mucor-type (Chongqing Yongchuan) and Aspergillus-type (Guangdong Yangjiang) (Hesseltine and Wang, 1972). If Douchi contains GLA it may be directly absorbed through diet. Thus, a low cost GLA production process could be achieved in fermented Douchi. The value-added fermented product containing GLA can alternate the traditional plant oils and become a good kind of healthy food for people. However, preliminary experiment of GLA in commercial Douchi from local supermarkets sample did not contain GLA. This apparently implied that GLA content in Douchi varied...

Background:Microwave-assisted reflux extraction of polysaccharides YPF-P from the famous Chinese traditional drug, Yupingfeng powder, optimization of extracting conditions and evaluation of their antioxidant activity were conducted in this study.Results:Single factor effect trends were achieved through yields and contends of YPF-P obtained from different extracting conditions. Then through a three-level, four-variable Box-Behnken design of response surface methodology adopting yield as response, the optimal conditions were determined as follows: Material/solvent ratio 1:23.37, microwave power 560 W, Extraction temperature 64°C, and extraction time 9.62 min. Under the optimal conditions, the YPF-P extraction yield was 3.23%, and its content was detected as 38.52%. In antioxidant assays, the YPF-P was tested to possess 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activities with an IC50 value of 0.262 mg/ml. In addition, YPF-P was also proved to have relatively low ferric reducing antioxidant power (FRAP), compared to Vc, through FRAP assay.Conclusion:In the microwave assisted reflux extraction research, good YPF-P yield was achieved from materials with relatively low YPF-P content. And for the first time, both DPPH and FRAP assays were conducted on YPF-P, which proved that the antioxidant activity of YPF-P contributed to the functions of this medicine.

The objective was to screen for and isolate a novel enzyme with the specific activity of a Δ6-fatty acid desaturase from Rhizopus oryzae. In this study, R. oryzae was identified as a novel fungal species that produces large amounts of γ-linolenic acid. A full-length cDNA, designated here as RoD6D, with high homology to fungal Δ6-fatty acid desaturase genes was isolated from R. oryzae by using the rapid amplification of cDNA ends method. It had an open reading frame of 1176 bp encoding a deduced polypeptide of 391 amino acids. Bioinformatics analysis characterized the putative RoD6D protein as a typical membrane-bound desaturase, including three conserved histidine-rich motifs, a hydropathy profile, and a cytochrome b5 -like domain in the N terminus. When the coding sequence was expressed in the Saccharomyces cerevisiae strain INVScl, the encoded product of RoD6D exhibited Δ6-fatty acid desaturase activity that led to the accumulation of γ-linolenic acid. The corresponding genomic sequence of RoD6D was 1565 bp in length, with five introns. This is the first report on the characterization and gene cloning of a Δ6-fatty acid desaturase of R. oryzae from Douchi.