Microbiological and physico-chemical characteristic of Rwandese traditional beer “Ikigage”

Samples of traditional sorghum beer Ikigage was collected in the southern province of Rwanda and analyzed for microbiological and physico-chemical contents. Ikigage contained total aerobic mesophilic bacteria (33.55 x 106 cfu/ml), yeast (10.15 x 106 cfu/ml), lactic acid bacteria (35.35 x 104cfu/ml), moulds (4.12 x 104 cfu/ml), E. coli (21.90 x 103 cfu/ml), fecal streptococci (22.50 x 103 cfu/ml), Staphylococcus aureus (16.02 x 103 cfu/ml), total coliform (32.30 x 103 cfu/ml), ethanol, soluble protein,reducing sugars, total acidity, pH and Brix were 2.2% (v/v), 9.2 g/l, 2.3, 1.7%, 3.9 and 11.5 bx, respectively. The yeast was identified by API 20 C test and confirmed by PCR-Sequencing of ITS-5.8S region of rDNA. Seventy yeasts isolated in the samples were found to belong to either Saccharomyces cerevisae, Candida inconspicua, Issatchenkia orientalis, Candida magnolia and Candida humilis. Lactic acid bacteria were identified using the API 50 CHL system. Ten different isolates of lactic acid bacteriabelonged exclusively to the genus Lactobacillus: Lactobacillus fermentum, Lactobacillus buchneri, and Lactobacillus sp. The micro-organisms of fecal origin are from the water and the operations postfermentation process. The presence of potential pathogens emphasizes the importance of developing starter cultures with GRAS status for commercialization of ikigage

Optimization of extracellular catalase production from Aspergillus phoenicis K30 by a linear regression method using date flour as single carbon source and purification of the enzyme

Aspergillus phoenicis K30 is the selected mutant which produces an amount of extracellular catalase. To amplify the extracellular catalase production by the strain, a fermentation optimization was performed. To select the factors affecting the production, nine active variables (factors) consisting of 12 experiments were analyzed by Plackett-Burman design. Each variable was tested at two levels, a higher and a lower level. The studies of the effect of each variable and the establishment of a correlation between the response of enzyme activity and variables revealed that the link is a multiple linear regression form. The optimization was carried out through a simplex algorithm. The amount of extracellular catalase produced by the strain in the optimized medium was about four times higher than that obtained in non optimized medium corresponding to 3820 mg/L of extracellular proteins including 59500 U/L of extracellular catalase activity after 96 h of fermentation. The steps of purification were allowed to improve enzyme activity by 305-fold. From an analytical gel electrophoresis under native conditions, an apparent molecular mass of 158 kDa was determined suggesting that the enzyme is a homodimer. The isoelectric point of the protein was found to be 5 ± 0.1 as determined by a Pharmacia Phast-system.Keywords: Aspergillus phoenicis, extracellular catalase purification, dates flour, optimization, multiple linear regression.African Journal of Biotechnology Vol. 12(19), pp. 2646-265