Antifungal activity of different neem leaf extracts and the nimonol against some important human pathogens

This study was conducted to evaluate the effect of aqueous, ethanolic and ethyl acetate extracts from neem leaves on growth of some human pathogens (Aspergillus flavus, Aspergillus fumigatus, Aspergillus niger, Aspergillus terreus, Candida albicans and Microsporum gypseum) in vitro. Different concentrations (5, 10, 15 and 20%) prepared from these extracts inhibited the growth of the test pathogens and the effect gradually increased with concentration. The 20% ethyl acetate extract gave the strongest inhibition compared with the activity obtained by the same concentration of the other extracts. High Performance Liquid Chromatography (HPLC) analysis of ethyl acetate extract showed the presence of a main component (nimonol) which was purified and chemically confirmed by Nuclear Magnetic Resonance (NMR) spectroscopic analysis. The 20% ethyl acetate extract lost a part of its antifungal effect after pooling out the nimonol and this loss in activity was variable on test pathogens. The purified nimonol as a separate compound did not show any antifungal activity when assayed against all the six fungal pathogens.

Production of ethanol by alginate-entrapped Saccharomyces cerevisiae strain "14-12"

Cells of S. cerevisiae strain "14-12" of different ages were immobilized in sodium alginate and used for conversion of glucose to ethanol. Immobilized cells of 48 hr old were the most potential. Employment of high counts of alginate-entrapped cells shortened the period required for production of the maximal alcohol yield. However, the percentage surviving cells decreased with increasing initial cell counts. Maximal accumulation of ethanol (4.18 g/100 ml) was obtained after 4 days of static fermentation with 1.8 X 10(8) immobilized yeast cells. The residual viable cell count was found to represent 3-fold the surviving percentage in a control experiment using an inoculum of the free yeast cells. Immobilized yeast cells could convert about 85% of the available sugars to ethanol over 28 days of the repeated-batch fermentation. The immobilized cells retained 50% of their viability for 16 days. After 48 days of repeated fermentation only 6% of the yeast cells were viable, and on the 52nd day no viable cells could be detected.

Ethanol tolerance of Saccharomyces cerevisiae and its relationship to lipid content and composition

Saccharomyces cerevisiae strain 14-12 is a highly ethanol-tolerant organism. It can grow in the presence of 13% ethanol but growth is completely prevented at 14% ethanol. A relationship was detected between yeast lipids and ethanol tolerance. A gradual decrease of lipid content was recorded as the concentration of supplemented ethanol increased. Moreover, free fatty acids were comparatively decreased in these lipid extracts. When separately added to media with 14% ethanol different lipids produced varied stimulatory effects on yeast growth. Maximum yield of yeast growth was obtained at 14% ethanol in the presence of lecithin, palmitic acid and cholesterol. Yeast lipids produced in the presence of these fractions are characterized by a relatively high percentage of free fatty acids. The change in the percentage of free fatty acids was shown to be the controlling factor in ethanol tolerance.