No abstract

T HE ANTIBACTERIAL potential of Ziziphus-spina christi as methanol and ethanol extracts, of bark, fruit, roots, seeds and leaves, were evaluated against seven pathogenic bacterial strains using agar well diffusion technique: The used strains were Pseudomonas aeruginosa (ATCC 278223), Enterobacter cloacae (ATCC 13047), Enterobacter aerogenes (ATCC 13084), Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13888), Enterococcus faecalis (ATCC 29212) and Methicillin-resistant Staphylococcus aureus (MRSA, ATCC 43300). The antibiotic erythromycin was used as positive control. The presence of phytochemical compounds in the extracts was determined qualitatively, the functional bioactive groups were characterized by FTIR and the presence of bioactive elements was characterized by XRF. Antibacterial activity against the used bacterial strains was assessed by determining the minimal inhibitory and bactericidal concentrations (MIC and MBC) assays. All the used Gram negative and positive bacteria were sensitive to various plant extracts. Bark extract was the most active against all strains except for Enterobacter aerogenes. Ethanol bark extract showed great activity against Enterococcus faecalis with 16.2 mm clearing zone and MIC, MBC of 15 and 20 mg ml -1 , respectively. Methanol bark extract was also effective against Klebsiella pneumoniae with a clearing zone of 16.2 mm and 20 mg ml -1 for both MIC, MBC. Leaves extracts showed high antibacterial activity against all strains except Escherichia coli. Ethanol fruit extract also exhibited high activity against Pseudomonas aeruginosa with 20 mm clearing zone and 2.5, 10 mg ml -1 for both MIC and MBC. Finally, ethanol roots showed the largest clearing zone against Enterococcus faecalis (21mm) with 10 and 15 mg ml -1 for MIC and MBC, respectively.

No abstract

The xylanolytic and amylolytic yeasts were qualitatively determined by Cong red xylan agar and soluble starch agar plates, respectively. The most xylanase and α-amylase inducible strain (AUN-02) was selected and identified using PCR amplification of 26S rRNA gene and sequence analysis. The comparison of the alignment results and phylogenetic analysis of the sequences of the isolated yeast to published rRNA gene sequences in GenBank, confirmed the identification of the isolate as Pichia membranifaciens. Xylanase and α-amylase production by isolated P. membranifaciens were investigated at different pH values (4-8), temperature degrees (20-45°C), incubation time (1-7 days) and various substrates.A higher production of xylanase (38.8 U/mL) and a-amylase (28.7 U/mL) was obtained after 4 days of fermentation of P. membranifaciens. Higher activity of xylanase (36.83 U/mL) and a-amylase (27.7 U/mL) was obtained in the fermentation of P. membranifaciens in a culture medium adjusted to pH 7.0. The optimum temperature showed maximum xylanase and a-amylase activity (42.6 and 32.5 units/mL, respectively) was estimated at 35 °C. The xylanase and a-amylase activities of P. membranifaciens were estimated and compared for the different substrates tested. The strain revealed 100% relative activity of xylanase and a-amylase on beechwood and potato starch, respectively. The affinity of enzymes towards substrate was estimated using Km values. The Km values of xylanase and α-amylase increased in the order of pH’s 7.0, 6.0 and 4.5 (0.85, 1.6 and 3.4 mg xylan/mL and 0.22, 0.43 and 2.8 mg starch/mL, respectively). the yeast P. membranifaciensis is suitable for produce neutral xylanase and α-amylase enzymes. So, it could be used as a promising strain for production of these enzymes in industrial field.

No abstract