We constructed and characterized a Xanthomonas campestris pv. phaseoli oxyR mutant. The mutant was hypersensitive to H2O2 and menadione killing and had reduced aerobic plating efficiency. The oxidants’ induction of the catalase and ahpC genes was also abolished in the mutant. Analysis of the adaptive responses showed that hydrogen peroxide-induced protection against hydrogen peroxide was lost, while menadione-induced protection against hydrogen peroxide was retained in the oxyR mutant. These results show that X. campestris pv. phaseoli oxyR is essential to peroxide adaptation and revealed the existence of a novel superoxide-inducible peroxide protection system that is independent of OxyR.

Medium optimization for production of polyb-hydroxyalkanoate (PHA) from Rhodobacter sphaeroides U7 cultivated in glutamate-acetate (GA) medium supplemented with 40 mM valeric acid as co-substrate under aerobic-dark condition was investigated. Studies on effect of nitrogen source and cultivation temperature by conventional and statistical methods illustrated that (NH 4 ) 2 SO 4 (0.2 g/l) had no effect and the optimal temperature was at 30°C. The optimum environmental conditions were found to be anaerobic-light (3000 lux) cultivation with aeration rate of 1.0 vvm and agitation speed of 200 rpm for PHA production (2.5 g/l) with the highest PHA content (65.15%) at 0.5 vvm, and 200 rpm. Under this optimized medium and condition, PHA production from R. sphaeroides U7 increased 3.86-folds (from 0.69 to 2.66 g/l) (PHA content increased 1.5-folds). The biopolymer was purified and characterized by using 13 C NMR, FTIR, DSC, X-ray diffraction and intrinsic viscosity techniques to be a copolymer poly(b-hydroxybutyrate-co-b-hydroxyvalerate) (PHBV) consisting of 84.8 mol% b-hydroxybutyric acid (HB) and 15.2 mol% b-hydroxyvaleric acid (HV).

In this contribution the synthesis of phosphatidylserine (PS) using a phospholipase D (PLD) produced by Streptomyces sp. isolated from soil-and wastewater-contaminated palm oil is shown. Streptomyces sp. SC734 was found to produce PLD in the culture medium and showed the highest transphosphatidylation activity. This PLD was purified and characterized. The purified PLD SC734 converted phosphatidylcholine (PC) to PS completely in a biphasic system consisting of chloroform and sodium acetate buffer (pH 6.0) at 1:5 (mol/mol) of PC to L-serine at 45°C within 40 min using 1.5 U PLD. The PLD could also synthesize PS from soybean lecithin with 100% conversion in the biphasic system at 1:7 (mol/mol) of soybean lecithin to L-serine at 45°C in 60 min. In addition, the PLD SC734 could be used to synthesize PS from soybean lecithin in an aqueous system as well with up to 94.7% conversion in the presence of 2.5 mM Triton X-100 in 100 min.

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A total of 2257 lactic acid bacteria were preliminarily screened for antagonistic activity against subsp. JCM 1157. Strain SKI19 was selected and identified at the subspecies level as subsp. SKI19, using rRNA gene sequence analysis combined with and genes' amplification. Antibacterial activity of SKI19 was completely lost after treatment of neutralized cell free culture supernatant with proteolytic enzymes, suggesting that SKI19 produced a bacteriocin-like substance that inhibited not only closely related species, but was also effective against DMST 17303. Viewed under scanning electron microscope, cell membranes of the indicator strain appeared to collapse after exposure to the bacteriocin-like substance. In vitro tests concerning probiotic properties, SKI19 survived under simulated gastrointestinal tract conditions, and adhesion of its cell surface to xylene and chloroform was 90.14 and 89.85%, respectively. Complete inhibition by SKI19 against pathogenic bacteria ( DMST 4212, DMST 17303, and DMST 8840) was observed in co-cultivation under anaerobic conditions. A safety assessment showed that SKI19 was susceptible to several antibiotics and had no haemolytic activity. PCR amplification of virulence factors with the specific primers for ,, , , , and genes were negative for SKI19. Also, SKI19 did not harbor any ,, or genes involved in biogenic amine production. The results reveal that SKI19 has probiotic potential and antibacterial activity, and is safe for further application in certain food products.