Microbial and chemical properties of Cambodian traditional fermented fish products.

BACKGROUND: Fermented fish products, commonly consumed in south-east Asia, are used as condiments that contribute to people's nutritional sources and as seasonings to improve food taste and flavour. Among these, the Cambodian products prahok (fish paste), kapi (shrimp paste) and toeuk trey (fish sauce) have not been examined in detail. This is the first study to investigate their chemical and microbial properties. RESULTS: Acetic acid was the most common organic acid with the highest concentration in 10/13 samples (1.9-26.6 g kg(-1)). Lactic acid was also found at high concentrations (0.4-12.9 g kg(-1)). 16S ribosomal RNA gene-dependent phylogenetic analyses indicated that Gram-positive cocci and rods, such as Bacillus, Clostridium, Staphylococcus and Tetragenococcus, were the major microbial populations. High sodium chloride concentrations detected in these products (170-270 g kg(-1)) could be responsible for inhibition of the growth of Gram-negative putrefactive microorganisms. CONCLUSION: This study established a relationship between the chemical and microbial compositions of Cambodian fermented fish products, which provides a basis for preservation and maturation. These data could be beneficial in the manufacturing of these products in terms of microbial control and quality stabilisation.

Isolation and characterization of antifungal substances from Burkholderia sp. culture broth.

A new antagonistic Burkholderia strain, designated MP-1 and producing antifungal activities against various filamentous plant pathogenic fungi, was isolated from the rhizoshere in the Naju area. Cultural characteristic studies strongly suggested that this strain belongs to the genus Burkholderia. The nucleotide sequence of the 16S rRNA gene (1491 pb) of strain MP-1 exhibited close similarity (99% to 100%) with other Burkholderia 16S rRNA genes. Extraction of fermentation broth of Burkholderia sp. MP-1 and various separations and purification steps led to isolation of four pure active molecules. The chemical structure of these four compounds-named phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid, and 4-hydroxyphenylacetate methyl ester-was established on the basis on their gas chromatography-electron impact-mass spectrometry (GC-EI-MS) and trimethylsilation GC-EI-MS data. The four isolated compounds inhibited filamentous fungal growth on potato dextrose agar medium supplemented with 100 mg/L of phenylacetic acid, hydrocinnamic acid, 4-hydroxyphenylacetic acid and 4-hydroxyphenylacetate methyl ester individually.