Microbiological characteristics of four samples of bio-extract from gamma irradiated (300 kGy) silk waste ferrmented for 0, 1, 2, 3 and 4 months were investigated. The results revealed that total bacterial counts in all samples of bio- extract were initially found to be 2.32×107 – 1.69×108 cfu/ml. Four months later, total bacterial counts mainly decreased according to the fermentation time. At the beginning, lactic acid bacteria were found in three samples and ranged from 6.0×106–2.2×108 cfu/ml. Only in one sample that lactic acid bacteria were not found. Four months later, lactic acid bacteria were still found in two samples and ranged from 1.8×102–3.8×107 cfu/ml. Initially, total yeasts were found in all samples and ranged from 1.0×104–3.2×105 cfu/ml which exceeded the standard value of Thai Community Product Standard : Plant Extraction [TCPS 481-2547(2004)]. In the fourth month, total yeasts were not found in three samples. However, they were found in one sample and still exceeded the standard value. Three pathogenic bacteria (Salmonella spp., Staphylococcus aureus and Clostridium perfringens) based on the TCPS 481-2547(2004), were not found in any samples after any fermentation length. At zero month, all samples were contaminated with Escherichia coli densities in the range of 15 – >1.1x103 MPN/ml and exceeded the standard value of TCPS 481-2547(2004). However, one month later the MPN of E. coli were not found in all samples and therefore the samples were up to the standard level of TCPS 481-2547(2004).
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