Biocontrol Science
Online ISSN : 1884-0205
Print ISSN : 1342-4815
ISSN-L : 1342-4815
14 巻 , 3 号
Original papers
    2009 年 14 巻 3 号 p. 87-95
    発行日: 2009年
    公開日: 2010/01/26
    ジャーナル フリー
    Neosartorya and Talaromyces are typical fungi capable of producing heat resistant ascospores responsible for the spoilage of processed fruit products. In this study, the heat activation rates of Neosartorya and Talaromyces ascospores were investigated in several suspending media at various heating temperatures. Ascospores were dispersed in pH 3.5 McIlvain buffer, organic acid/alcohol-supplemented McIlvain buffer and grape juice (pH 3.5, 5.0°Brix) prior to heat treatments. In McIlvain buffer, the number of germinating ascospores increased logarithmically with longer exposure to heating at all test temperatures. Heat activation rates (k values) accelerated with increasing temperature. The calculated activation energy (Ea) values were similar among ascospores from the same genus, but the Ea of the test Neosartorya spp. were greater than that of the test Talaromyces spp. Greater k values were calculated from acetate-supplemented McIlvain buffer and grape juice. Similarly, normal- and branched-chain fatty acids were shown to enhance the heat activation rate of the ascospores in McIlvain buffer systems. These results could assist the food industry in designing adequate thermal processes for food products against the heat resistant fungi.
    2009 年 14 巻 3 号 p. 97-105
    発行日: 2009年
    公開日: 2010/01/26
    ジャーナル フリー
    An Alcanivorax dieselolei strain, termed strain N1203, was isolated from the consortia of ammonia-oxidizing bacteria (AOB) combined with denitrifying bacteria from our previous study and was shown to have ability to reduce nitrate to nitrite to either nitrous oxide or molecular nitrogen. Analysis of 16S rRNA gene sequences established strain N1203 as a member of the species Alcanivorax dieselolei. In addition, the ability of strain N1203 to utilize various organic substrates as the sole carbon source, supplemented with carbohydrates, amino acids, and n-alkane compounds, was investigated, and this strain was found to have a narrow substrate range of growth such as grycerol, succinate, ethanol and n-alkane hydrocarbon. Furthermore, N1203's stepwise denitrifying activity, utilizing succinate and hexadecane as sole carbon sources, was measured. Gene fragments of nirK and qnorB genes, which are involved in denitrifying activities, were obtained, cloned and sequenced. Phylogenetic analysis for these two genes showed that both the nirK and qnorB sequences, although found in separate branches within clusters, formed subclusters branching from uncultured environmental clones. This demonstrated the typical uniqueness of these genes from any cultivated denitrifiers. Thus, strain N1203 is novel type of denitrifying bacteria that demonstrated denitrifying activities when cultivated using succinate as the sole carbon source.