Study on performance of ultrafiltration membrane-based pretreatment for application to seawater reverse osmosis desalination.

The objective of the work was to study at lab-scale the efficiency of hybrid process- coupling powdered activated carbon (PAC) adsorption or FeCl(3) coagulation and UF- for marine organic matter removal. Regenerated cellulose membrane with 30 kDa and actual seawater from Mediterranean Sea were used. The coagulant was FeCl(3) and adsorbents were two PAC types, with different surface area and pore size distribution. The results showed that PAC adsorption/UF performed higher efficiency in terms of organic removal than FeCl(3) coagulation/UF. Organic matter removal up to 50% was obtained for a PAC dose of 200 mg/L. According to high performance size exclusion chromatography (HP-SEC) analysis, the organics removed by PAC/UF are approximately 10 kDa. Therefore, the effect of PAC adsorption was deeply evaluated in terms of UF membrane fouling rate. The fouling rate was reduced when increasing PAC dose for both PAC types, in particular when PAC with a higher BET surface area and larger fraction of micropores was used. On the other hand, the results showed that UF unit could highly reduce SDI(3) from 26 to 9. The addition of PAC and FeCl(3) to UF allowed a further reduction of SDI(3) from 9 to 4-6.

Exopolysaccharide-producing lactic acid bacteria strains from traditional Thai fermented foods: isolation, identification and exopolysaccharide characterization.

Lactic Acid Bacteria (LAB) isolated from various traditional Thai fermented foods were screened for exopolysaccharides (EPS) production. From 104 isolates, two rod-shaped and five coccal-shaped LAB were able to produce EPS from sucrose on solid media. However, only the cocci were capable of producing EPS in liquid media and these were identified as Pediococcus pentosaceus. Pediococcus pentosaceus strains AP-1 and AP-3 produced EPS in high yield. In liquid media containing sucrose as carbon source, the amount of EPS produced by AP-1 and AP-3 strains was 6.0 and 2.5 g/L, respectively. The isolated and purified EPSs were chemically characterized. On the basis of sugar composition, methylation analysis and nuclear magnetic resonance spectroscopy, both the EPSs were shown to belong to the same dextran class. In particular, both EPSs differed from linear dextran by branching through 3,6-di-Osubstituted alpha-D-glucopyranosyl residues. The EPS from P. pentosaceus AP-3 was characterized by a relatively higher degree of branching and by a higher molecular weight than that from P. pentosaceus AP-1.