Browsing by Author "Germain T. Karou"

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    Implication of Bacillus sp. in the production of pectinolytic enzymes during cocoa fermentation
    (2008) Abdourahamane Sangare; Ban L. Koffi; Germain T. Karou; Honore G. Ouattara; Sebastien L. Niamke; Jacques K. Diopoh
    The role of bacilli in cocoa fermentation is not well known. Their potential of production of pectinolytic enzymes during this process was evaluated. Bacillus growth was monitored and pectinolytic strains were screened for their use of pectin as sole carbon source. Effects of cocoa fermentation parameters susceptible to influence on enzyme production were analysed. Among 98 strains isolated, 90 were positive for pectin degradation and 80% of them presented detectable pectinolytic activities in submerged fermentation. Forty-eight strains produced polygalacturonase (PG), 47 yielded pectin lyase (PL) and 23 strains produced both enzymes. Bacilli growth was not significantly affected during fermentation. PL production was favoured by galactose, lactose, glucose as sugars, and arginine, glutamine, cysteine and ammonium sulphate as nitrogen compounds. Pectin at low concentration (0.05%) and iron stimulated PL production. It was strongly repressed by galacturonic acid (1%), and negatively affected by nitrogen starvation, zinc and temperatures above 45 C. PL yield was very weak below pH 4.0 and in anaerobic conditions. PG production was weakened by sucrose and cation depletion. It was increased slightly by cysteine, ammonium nitrate and nitrogen starvation and significantly above 40 C. PG synthesis was not affected by acidic pH (3.0–6.0) or oxygen availability. As fermentation products, lactate and acetate lowered the production of both enzymes while ethanol had no effect. The high proportion of pectinolytic producers among the strains studied and analysis of factors influencing pectinolytic enzymes production, suggest that Bacillus sp. is liable to produce at least one enzyme during cocoa fermentation.