Bacteriocin-producing lactic acid bacteria (LAB) were isolated and screened from the gastrointestinal tract (GIT) of Thai indigenous chickens. The bacteriocinogenic activities and the primary probiotic properties were determined. The bacteriocins produced by 14 strains of selected LAB displayed inhibitory activity against indicator strains after the supernatants were neutralized with NaOH in the following species: Lactobacillus sakei subsp. sakei JCM1157, Enterococcus faecalis VanB, Bacillus sp., and Listeria monocytogenes. The antagonistic activity of selected LAB was inactivated or decreased after being treated with proteolytic enzymes (α-chymotrypsin and trypsin). CR5-1 strain exhibited the highest level of activity (5120 AU/ml) in the stationary phase against L. sakei subsp. sakei JCM1157 in MRS broth at 37°C. The nine isolates of selected LAB were investigated for primary probiotic properties. The survival of the nine isolates was found to decrease approximately by 3 log CFU/ml after passing through the gastrointestinal conditions. All isolates exhibited protein digestion on agar plates but no isolates showed the ability to digest starch and lipid. Most of them showed high susceptibilities to some antibiotics (penicillin G, tetracycline and erythromycin). Thirteen LAB strains producing bacteriocin with strongly inhibitory activity were identified as Lactobacillus salivarius and only one strain was identified by 16S rDNA sequence analysis as Lactobacillus agilis.

ABSTRACT:A bacteriocin-like substance (BLS) producing Enterococcus faecium CE5-1 was isolated from the gastrointestinal tract (GIT) of Thai indigenous chickens. Investigations of its probiotic potential were carried out. The competition between the BLS probiotic strain and antibiotic-resistant enterococci was also studied. Ent. faecium CE5-1 exhibited a good tolerance to pH 3.0 after 2 h and in 7% fresh chicken bile after 6 h, but the viability of Ent. faecium CE5-1 decreased by about 2-3 log CFU/ml after 2 h incubation in pH 2.5. It was susceptible to the antibiotics tested (tetracycline, erythromycin, penicillin G, and vancomycin). The maximum BLS production from Ent. faecium CE5-1 was observed at 15 h of cultivation. It showed activity against Listeria monocytogenes DMST17303, Pediococcus pentosaceus 3CE27, Lactobacillus sakei subsp. sakei JCM1157, and antibiotic-resistant enterococci. The detection by polymerase chain reaction (PCR) in the enterocin structural gene determined the presence of enterocin A gene in Ent. faecium CE5-1 only. Ent. faecium CE5-1 showed the highest inhibitory activity against two antibiotic-resistant Ent. faecalis VanB (from 6.68 to 4.29 log CFU/ml) and Ent. gallinarum VanC (from 6.76 to 4.31 log CFU/ml) after 12 h of co-cultivation. The results show the future possible use of Ent. faecium CE5-1 as a probiotic strain for livestock to control antibiotic-resistant enterococci.

This is the first report on the possible use of decanter cake waste (DCW) from palm oil industry as alternative nutrient sources and biomass support particles for whole-cell lipase production under solid-state fermentation (SSF) by newly isolated fungal Aspergillus sp. MS15 and their application as a low-cost and environment-friendly biocatalyst for biodiesel production. The results found that DCW supplemented with 0.1% K2HPO4, 0.05% MgSO4·7H2O, 1% peptone and 2% urea and pH adjusted to 6.0 was optimal for whole-cell lipase production. The optimal moisture content and fermentation temperature was 60% and 37.5 °C, respectively. Environmentally friendly biodiesel production, through either esterification or transesterification using whole-cell lipase immobilized on DCW as a biocatalyst, was optimized. The optimal reaction temperature for both reactions was 37 °C. The whole-cell lipase effectively esterified oleic acid into >95% biodiesel yield through esterification under optimal water activity at 0.71 and an optimal methanol to oleic acid molar ratio of 2:1, and also effectively transesterified palm oil under optimal water activity at 0.81 and an optimal methanol to oil molar ratio of 3:1. The fuel properties of produced biodiesel are close to the international biodiesel standards. These results have shown the circular utilization of palm oil mill waste for the low-cost production of an effective biocatalyst, and may contribute greatly to the sustainability of renewable bioenergy production.