Subcritical water treatment of defatted rice bran to produce functional food materials

Abstracts / Journal of Bioscience and Bioengineering 108 (2009) S135–S146 FE-P6 Growth-inhibitory activity of antimicrobial peptides from rice against oral pathogenic bacteria and clarification of their action mechanism Tomoaki Kouya,1 Yusuke Koiso,2 Mayumi Taiyouji,2,3 Sadami Ohtsubo,3 Takaaki Tanaka,2,4 and Masayuki Taniguchi2,4 Food Science Center, Niigata University, Niigata, Japan 1 Department of Advanced Materials Science and Technology, Graduate School of Science and Technology, Niigata, Japan 2 Food Research Center, Niigata Agricultural Research Institute, Niigata, Japan 3 and Department of Materials Science and Technology, Faculty of Engineering, Niigata, Japan 4 Antimicrobial peptides are important components of host defense system in animals, plants, and microorganisms. A large number of antimicrobial peptides have been isolated from various organisms, which have widely antibiotic potency against pathogenic microorganisms. The antimicrobial peptides have common feature as follows; amphiphilicity, membrane permeability, and positive net charge. Some bioactive proteins such as enzymes and inhibitors have been isolated from rice (1). Recently, we found that a synthetic peptide (CH 14–25: 12 amino acids) derived from a rice protein (cyanate hydratase: CH) had antimicrobial activity. In this study, to utilize CH 14–25 as a functional food material, the antimicrobial activity of CH 14–25 against Porphyromonas gingivalis, a major periodontal pathogen, was investigated. Fifty percent growthinhibitory concentration (IC50) was determined on the basis of the results of antimicrobial activity assay using ATP-bioluminescence reaction. The IC50 was found to be about 200 μg/mL. Moreover, the antimicrobial activity of fragments and mutants of CH 14–25 was determined to examine the contribution of each amino acid to the antimicrobial activity against P. gingivalis. The antimicrobial activity of CH 15–25, a truncated form without arginine residue (a N-terminal amino acid of CH 14–25) was lower than that of CH 14–25, suggesting that the N-terminal arginine residue plays an important role for expression of the antimicrobial action of CH 14–25. To examine the action mechanism of CH 14–25, we carried out the membrane depolarization assay using a potential-sensitive probe (diSC3(5)). The assay system showed that CH 14–25 depolarizes the cell membrane to inhibit the growth of P. gingivalis cells. Reference 1. Ohtsubo, S., Kobayashi, H., Noro, W., Taniguchi, M., and Saitoh, E.: Molecular cloning and characterization of oryzacystatin-III, a novel member of phytocystatin in rice (Oryza sativa L. japonica), J. Agric. Food Chem., 53, 5218-5224 (2005).

doi:10.1016/j.jbiosc.2009.09.024

FE-P7 Subcritical water treatment of defatted rice bran to produce functional food materials Shuji Adachi, Tze Loon Neoh, and Takashi Kobayashi Division of Food Science and Biotechnology, Graduate School of Agriculture, Kyoto University, Sakyo-ku, Kyoto, Japan Rice bran is a major by-product obtained from the polishing process that produces white rice. About 800,000 tons of rice bran is produced a year in Japan. Because it contains ca. 18% lipids, 400,000

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tons of rice bran is used for producing 60,000 tons per year of rice bran oil in Japan. The defatted rice bran has very low value and is generally used for reducing the cost of animal feed or discarded as agricultural waste. However, it still contains useful substances such as phenolic compounds having antioxidative, ultraviolet absorbing, and antitumor activities. Therefore, the defatted rice bran is promising for producing functional substances. In this context, the defatted rice bran was treated with subcritical water in the temperature range of 180 °C to 280 °C for 5 min using 117-mL and 9-mL vessels to produce the extracts. The total sugar and protein contents and radical scavenging activity of the extracts were then estimated for both vessels. The total sugar concentration of ca. 0.3 g/L-extract was the highest for the extracts at 200 °C, and it significantly decreased at the higher temperatures. The protein concentration and radical scavenging activity were higher at the higher temperatures. Extraction was also done at 200 °C and 260 °C for various times using the small vessel. The total sugar concentration decreased with the increasing extraction time, while the protein concentration and radical scavenging activity only slightly depended on the extraction time. The extracts at 200 °C or lower temperatures using the large vessel possessed the emulsifying and emulsion-stabilizing activities. The extract at 260 °C for 5 min exhibited suppressive ability for the oxidation of linoleic acid. doi:10.1016/j.jbiosc.2009.09.025

FE-P8 Establishment of optimal conditions for extracting protein fractions inhibiting arg-gingipain from polished rice Tsuyoshi Asakura,1 Tomoaki Kouya,2 Mayumi Taiyouji,3,4 Sadami Ohtsubo,4 and Masayuki Taniguchi3 Venture Business Laboratory, Niigata University, Niigata, Japan 1 Food Science Center, Niigata University, Niigata, Japan 2 Gaduate School of Science and Technology, Niigata University, Niigata, Japan 3 and Food Research Center, Niigata Agricultural Research Institute, Niigata, Japan 4 Aim: Porphyromonas gingivalis, a major periodontal pathogen, uptakes nutrients from host by secreting extracellular proteases. Of the proteases produced by P. gingivalis, Arg-gingipain (Rgp), a cysteine protease, is a major virulence factor. Recently, we found that polished rice contains the protein components capable of inhibiting Rgp activity. In this study, we investigated the optimum conditions for extraction of Rgp-inhibitory components from polished rice to develop a material for functional foods. Methods: Rice proteins were extracted from rice powder (5 g) with ten times volume (50 ml) of water or buffer for 30 min at room temperature. Then, the resultant suspension was centrifuged at 15,000×g for 20 min. The supernatant was heated for 30 min at 95 °C, and cooled on ice, followed by centrifugation at 15,000 × g for 20 min. Results: When Rgp-inhibitory fractions were extracted from rice powder with water, the dry weight of extract and its inhibitory activity were 7.5 (g/kg rice powder) and 5.7 (mU/mg protein), respectively. The results of SDS-PAGE and gel chromatography showed that the molecular weights of inhibitory components are between 15 and 30 kDa. In the extraction with saline solutions, the total inhibitory activity of the extract was gradually increased with increase in NaCl concentration until 200 mM. The total inhibitory activity of the extract prepared with citrate buffer (pH 6.0) was 6 times as high as that with water. However, no synergistic effect on extraction of the total inhibitory activity was observed between salt solution and citrate buffer. When the extract was not treated by heat,