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AIM:To investigate the antioxidant activity of chitooligosaccharides (COSs) on pancreatic islet cells in diabetic rats induced by streptozotocin. METHODS:The antioxidant effect of COSs on pancreatic islet cells was detected under optical microscopy and with colorimetric assay and gel electrophoresis. The activities of glutathione peroxidase and superoxide dismutase, total antioxidant capacity, and content of malondialdehyde in serum and tissue slices of pancreas were examined after 60 d to determine the effect of COSs in streptozotocin-induced diabetes in rats. RESULTS:COSs can prohibi t the apoptosis of pancreatic islet cells. All concentrations of COSs can improve the capability of total antioxidant capacity and activity of superoxide dismutase and decrease the content of malondialdehyde drastically. Morphological investigation in the pancreas showed that COSs have resulted in the reduction of islets, loss of pancreatic cells, and nuclear pyknosis of pancreatic cells. CONCLUSION:COSs possess various biological activities and can be used in the treatment of diabetes mellitus.

BACKGROUND: Xylitol, a sugar alcohol widely used in food and pharmaceutical industries, can be produced through biological reduction of xylose present in hemicellulose hydrolysates by Candida tropicalis. However, the aeration rate and by-products originating from hemicellulose hydrolysis strongly inhibit the production of xylitol in a fermentation process. A two-stage fed-batch fermentation system was developed to reduce these inhibitory effects and to improve xylitol production from corn cob hemicellulose hydrolysates by C. tropicalis.

BACKGROUND: Saccharomyces cerevisiae is one of the main microorganisms that can produce S‐adenosylmethionine (SAM) from L‐methionine and ATP with high productivity. To satisfy the ATP requirement for SAM synthesis, sufficient oxygen should be supplied to the medium to improve aerobic metabolism in S. cerevisiae. In this study, n‐hexadecane used as oxygen vector for enhancement of SAM production by this yeast was investigated.RESULTS: N‐hexadecane was most favorable for cell growth and SAM synthesis in S. cerevisiae when added at the time of inoculation. It could increase glucose consumption, reduce ethanol accumulation, and ultimately improve biomass and SAM productivity in a fermentation process. In a bioreactor, the highest yield of SAM (2.27 g L−1) was achieved in the presence of 4% (v/v) n‐hexadecane after 24 h of inoculation, which was 23.37% higher than the control (1.84 g L−1).CONCLUSION: The addition of n‐hexadecane to cultures of S. cerevisiae significantly enhanced SAM production without increasing energy consumption, and has the potential for use in large‐scale fermentation processes to increase oxygen supply. Copyright © 2012 Society of Chemical Industry