Mutageneisis of xanthomonas campestris and selection of strains with enhanced xanthan production

Xanthan gum is a microbial polysaccharide of great commercial importance as it has unusual rheological properties in solution and consequent range of applications. In this study, a series of mutants were isolated from Xanthomonas campestris PTCC 1473 by ethyl methanesulfonate mutagenesis. The polysaccharide yield of one mutant, XC1473E2, was 30% better than that of the parent strain. It also showed higher xanthan formation and glucose consumption rates compared to the parent strain. Xanthan produced by the mutant had enhanced viscosity, higher pseudoplasticity and larger molecular weight. Since mutant XC1473E2 appeared white on agar plates, it underwent pigment extraction with methanol. Contrary to the parent strain, the mutant showed no absorption at 443nm, i.e. the wavelength related to yellow pigment. This finding suggested that yellow pigmentation and normal xanthan biosynthesis are not necessarily concurrent. In general, mutant XC1473E2 seems to be a strain with interesting characteristics for use in commercial production of xanthan

Antagonism of Yeasts to Xanthomonas Campestris PV. Campestris on Cabbage Phylloplane in field

Twenty yeast isolates, obtained from cabbage phylloplane, were evaluated for antagonistic activity against Xanthomonas campestris pv. campestris, in field. Plants of cabbage ev. Midori were pulverized simultaneously with suspensions of antagonists and pathogen. After 10 days, plants were evaluated through percentage of foliar area with lesions. Percentage of disease severity reduction (DSR per cent) was also calculated. Yeast isolates LR32, LR42 and LR19 showed, respectively, 72, 75 and 79 (per cent) of DSR. These antagonists were tested in seven different application periods in relation to pathogen inoculation (T1=4 d before; T2=simultaneously; T3=4 d after; T4=4 d before + simultaneously; T5=4 d after + simultaneously; T6=4 d before + 4 d after; T7=4 d before + simultaneously + 4 d after). The highest DSRs were showed by LR42 (71 per cent), LR42 (67 per cent), LR35 (69 per cent) and LR19 (68 per cent) in the treatments T7, T4, T5, and T6, which significantly differed from the others. The same yeast antagonists were also tested for back rot control using different cabbage cultivars (Fuyutoyo, Master-325, Matsukaze, Midori, Sekai I and Red Winner). The DSRs varied from 58 to 61 (per cent), and there was no significant difference among cultivars

Xanthan Production by Xanthomonas campestris in a whey-based medium

Isodados de Xanthomonas campestris foram adaptados à utilizaçäo de lactose para produçäo de xantana. Um meio mínimo de soro de leite (sem desproteinizaçäo e hidrólise) foi desenvolvido contendo 0,5 por cento K2HPO4; 0,01 por cento MgSO4 e 4 por cento leite gerando 14Kg/10 de goma. A viscosidade de soluçöes das gomas obtidas pelos isolados também foi avaliada

Producción de gomas xánticas / Production of xanthan gums

En el período que va desde febrero has agosto de 1990, se realizó un relevamiento de Xanthomonas campestris en la zona de Luján, provincia de Buenos Aires, de 70 muestras de vegetales infectados. Se comprobó si las 50 cepas de Xanthomonas campestris obtenidas presentaban la capacidad de producir goma xantan, así como el porcentaje de conversión de sustrato en goma y el recuento de Xanthomonas campestris viables/ml de cultivo. Los mayores números de cepas productoras del polisacárido extracelular se obtuvieron de alfalfa. Asimismo, la Xanthomonas campestris pv. alfalfae presentó elevados números de células viables y porcentajes de conversión de glucosa en goma xántica