Hydrogen sulfide (H2S) is a toxic and corrosive component that commonly occurs in biogas. In this study, H2S removal from swine-waste biogas using sulfur-oxidizing Paracoccus versutus CM1 immobilized in porous glass (PG) and polyurethane foam (PUF) biofilters was investigated. Bacterial compositions in the biofilters were also determined using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE). The biofilters were first tested on a laboratory scale under three space velocities (SV): 20, 30, and 40 h−1. Within 24 h, at an SV of 20 h−1, PG and PUF biofilters immobilized with P. versutus CM1 removed 99.5% and 99.7% of H2S, respectively, corresponding to the elimination capacities (EC) of 83.5 and 86.2 gm−3 h−1. On a pilot scale, with the horizontal PG-P. versutus CM1 biofilter operated at an SV of 30 h−1, a removal efficiency of 99.7% and a maximum EC of 113.7 gm−3 h−1 were achieved. No reduction in methane content in the outlet biogas was observed under these conditions. The PCR-DGGE analysis revealed that Paracoccus, Acidithiobacillus, and Thiomonas were the predominant bacterial genera in the biofilters, which might play important roles in H2S removal. This PG–P. versutus CM1 biofiltration system is highly efficient for H2S removal from swine-waste biogas.

Kombucha bacterial cellulose (KBC), a by-product of kombucha fermentation, can be used as a biomaterial for microbial immobilization. In this study, we investigated the properties of KBC produced from green tea kombucha fermentation on days 7, 14, and 30 and its potential as a protective carrier of Lactobacillus plantarum, a representative beneficial bacteria. The highest KBC yield (6.5%) was obtained on day 30. Scanning electron microscopy showed the development and changes in the fibrous structure of the KBC over time. They had crystallinity indices of 90–95%, crystallite sizes of 5.36–5.98 nm, and are identified as type I cellulose according to X-ray diffraction analysis. The 30-day KBC had the highest surface area of 19.91 m2/g, which was measured using the Brunauer–Emmett–Teller method. This was used to immobilize L. plantarum TISTR 541 cells using the adsorption–incubation method, by which 16.20 log CFU/g of immobilized cells was achieved. The amount of immobilized L. plantarum decreased to 7.98 log CFU/g after freeze-drying and to 2.94 log CFU/g after being exposed to simulated gastrointestinal tract conditions (HCl pH 2.0 and 0.3% bile salt), whereas the non-immobilized culture was not detected. This indicated its potential as a protective carrier to deliver beneficial bacteria to the gastrointestinal tract.

Microbial Enhanced Oil Recovery (MEOR) is an effective alternative method for oil recovery in reservoirs using microorganisms or their secondary metabolites. This research aimed to evaluate the indigenous bacteria from Mae Soon reservoir by culture-dependent and culture-independent methods and to investigate the potential of biosurfactant-producing bacteria using a drop-collapsed assay. Indigenous bacteria were isolated from the oil sands of the reserved core of Mae Soon reservoir using fi ve different media (nutrient, Luria-Bertani, mineral salt, tryptic soy, and peptone yeast extract). Fifty-four facultative anaerobic bacterial isolates were obtained. Seven isolates showed their potential as biosurfactant producers in the drop-collapse assay. Based on 16S rRNA gene analysis, six of the biosurfactant-producing bacterial isolates belonged to the species Bacillus licheniformis and one belonged to the species B. subtilis. The biosurfactant producers and microbial community in the oil sands were determined using Denaturing Gradient Gel Electrophoresis (DGGE). Interestingly, DGGE bands corresponding to bacteria belonging to the genus Geobacillus sp. were detected. Overall, the results obtained from this work showed that indigenous bacteria in Mae Soon reservoir oil well were prospective for use in MEOR.