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Machida T.,Laboratory of Food Hygienic Chemistry | Ohashi N.,Laboratory of Food Hygienic Chemistry | Mimura A.,Laboratory of Food Hygienic Chemistry | Honjoh K.-I.,Laboratory of Food Hygienic Chemistry | And 2 more authors.
Journal of the Faculty of Agriculture, Kyushu University | Year: 2010

Enhanced glucose 6-phosphate dehydrogenase (E.C., G6PDH) activity has been identified as a hardening-induced intracellular change of Chlorella vulgaris, which acquires freezing tolerance during hardening. In the present study, a full-length cDNA clone corresponding to a gene encoding a chloroplastic isoform of G6PDH, designated CvchG6PDH, was isolated from C. vulgaris C-27. By comparing the deduced amino acid sequence of CvchG6PDH with the N-terminal amino acid sequence of mature G6PDH 2 protein isolated previously, a DNA region encoding mature CvchG6PDH was determined and designated mCvchG6PDH. The deduced amino acid sequence of CvchG6PDH showed higher homology to those of plant plastidic G6PDH genes than those of cytosolic ones. A recombinant mCvchG6PDH protein expressed in Escherichia coli showed similar enzymatic properties to previously-isolated Chlorella G6PDH 2, suggesting that the gene encoded plastidic G6PDH 2 protein. Expression of CvchG6PDH was induced transcriptionally throughout 24-h hardening, while the translation was induced up to 9-h hardening and then decreased, and the change did not reflect the enhanced G6PDH activity during hardening. Furthermore, the mCvch-G6PDH alleviated both freezing and menadione-induced oxidative stresses in yeast. We showed the contribution of CvchG6PDH in menadione stress tolerance as one of its functions in the acquisition of freezing tolerance of Chlorella.

Soli K.W.,Laboratory of Food Hygienic Chemistry | Yoshizumi A.,Laboratory of Food Hygienic Chemistry | Yamakawa M.,Laboratory of Food Hygienic Chemistry | Mishima T.,Laboratory of Food Hygienic Chemistry | And 2 more authors.
Food Science and Technology Research | Year: 2011

Combined sequential treatment using 100 mg/L sucrose monopalmitate solution under microbubble generation and soaking in slightly acidic hypochlorous water containing 30 mg/L available chlorine for 5 min at 50°C was tested for decontamination of ginger, Japanese ginger, perilla, parsley, Welsh onion and cucumber, and at 20°C for strawberry. Viable bacterial count was reduced by about 2 log cfu/g in perilla, parsley, and Welsh onion. Ginger, parsley and Welsh onion maintained viable counts of less than 5 log cfu/ g during 6 days of subsequent cold storage at 6°C. Viable count for cucumber decreased by only 1 log cfu/ g after combined treatment, and increased to 5.5 log cfu/g after storage for 6 days at 6°C. For decontamination of strawberry, as 50°C treatment with SAHW damaged the surface, the treatment was performed at 20°C. After combined sequential treatment, viable bacterial count decreased from 4.5 to 2.0 log cfu/g, and increased slightly to 2.5 log cfu/g after storage at 6°C for 6 days. Fungal count for strawberry also decreased from 4.9 to 2.3 log cfu/g immediately after treatment and did not increase after storage for 6 days. These results indicate the great potential of this approach in sanitization of fresh fruits and vegetables.

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