• Environmental Engineering Research
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• v.20 no.2
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• pp.141-148
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• 2015

The presence of phenols in treated palm oil mill effluent (POME) is an environmental concern due to their phytotoxicity and antimicrobial activity. In this study, phenol-degrading bacteria, Methylobacterium sp. NP3 and Acinetobacter sp. PK1 were immobilized on oil palm empty fruit bunches (EFBs) for removal of phenols in the treated POME. The bacterial exopolysaccharides (EPS) were responsible for cell adhesion to the EFBs during the immobilization process. These immobilized bacteria could effectively remove up to 5,000 mg/L phenol in a carbon free mineral medium (CFMM) with a greater degradation efficiency and rate than that with suspended bacteria. To increase the efficiency of the immobilized bacteria, three approaches, namely activation, acclimation, and combined activation and acclimation were applied. The most convenient and efficient strategy was found when the immobilized bacteria were activated in a CFMM containing phenol for 24 h before biotreatment of the treated POME. These activated immobilized bacteria were able to remove about 63.4% of 33 mg/L phenols in the treated POME, while non-activated and/or acclimated immobilized bacteria could degrade only 35.0%. The activated immobilized bacteria could be effectively reused for at least ten application cycles and stored for 4 weeks at $4^{\circ}C$ with the similar activities. In addition, the utilization of the abundant EFBs gives value-added to the palm oil mill wastes and is environmentally friendly thus making it is attractive for practical application.

• Microbiology and Biotechnology Letters
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• v.52 no.2
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• pp.152-162
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• 2024

The microbial starter used to produce kefir beverages, kefir grain, contains a microbial exopolysaccharide called kefiran. Kefir grain consisting of water-insoluble polysaccharides, proteins, and fats, which can be applied as a multi-functional biopolymer. The mass of kefir grain can increase in the fermentation process of Kefir, but it is considered very slow. The purpose of this research is to study the impact of ammonium sulfate supplementation and yeast extract on reconstituted skim milk to increase the mass kefir grain and physical properties of kefiran. Results showed that the ammonium sulfate-supplemented substrate increased the mass of kefir grain by 547% in 14 days, with the condition that the substrate must be renewed every 2 days. Refreshing the substrate is considered one of the important factors. Supplementation on substrate did not appear to affect the viability of bacterial and yeast cells. Kefir grain produced from supplemented substrate also yields better thermal stability properties and has more functional groups than without supplementation. Two Lacticaseibacillus rhamnosus (RAL27 and RAL43) and one Limosilactobacillus fermentum (RAL29) were found to produce EPS. The three isolates also showed good skim milk fermentation ability after purification from kefir grain. The kefir grain produced in this study has the potential for wider application. This study also showed that kefir grain can be adjusted in quantity and quality through fermentation substrate engineering.

• Journal of the Korean Society of Food Science and Nutrition
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• v.42 no.1
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• pp.89-95
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• 2013

Biological and functional characteristics of lactic acid bacteria (LAB) were investigated in mustard stem/leaf kimchi (MK), cabbage kimchi (CK), young radish kimchi (YRK), and cubed radish kimchi (CRK). LAB of young radish kimchi were mainly composed of bacilli in contrast to the other kimchi. 89.2% LAB isolated from all kimchi harbored plasmids. However, LAB had an average of $4.1{\pm}0.5$ plasmid bands in YRK, more than MK, CK, and CRK. Exopolysaccharides were produced by 10.9~11.1% of LAB, and were especially by LAB isolated from radish kimchi. A significant percentage of LAB (69.5%) had antibacterial activity against one sensitive strain or more. LAB from CK, YRK and CRK had antimicrobial activities against Bacillus sp., Listeria monocytogenes, and Salmonella Typhimurium, while the LAB from MK had activities against Vibrio parahaemolyticus higher than those from the other kimchi. In YRK and CRK, acid-tolerant LAB were twice as prevalent as those in MK and CK. Bile-tolerant LAB isolated from CRK were more prevalent than other kimchi. When $10^8$ CFU of LAB were added to Caco-2 cells, 12.1% of LAB isolated from all kimchi showed similar adherent activity to Lactobacillus rhamnosus GG. LAB of MK particularly adhered to Caco-2 cells, 2.0~4.1 fold higher than LAB in the other kimchi. From these results, biological and functional characteristics of LAB varied according to the type of kimchi and LAB existing in kimchi were limited to their respective species.