Phytochemical and antimicrobial investigation of the leaves of five Egyptian mango cultivars and evaluation of their essential oils as preservatives materials.

The sterols, hydrocarbons and fatty acids constituents of the leaves of five mango cultivars locally implanted in Egypt were identified. The effect of their essential oils (EOs) against food borne microorganisms was studied as preservative materials. The chemical constituents of the EOs isolated from mango leaves were identified by Gas Chromatography-Mass spectrometry (GC-MS) technique. Trans-caryophyllene, α-humulene and α-elemene were identified as terpene hydrocarbons, while 4-hydroxy-4-methyl-2-pentanone as oxygenated compounds were recorded in all tested cultivars with variable amounts. Results showed that Staphylococcus aureus and Escherichia coli were the most sensitive microorganisms tested for Alphonso EOs. On the other hand, Salmonella typhimrium was found to be less susceptible to the EOs of the studied cultivars. The EOs of different mango cultivars induced a steady decrease in the activity of amylase, protease and lipase at the minimum inhibitory concentration (MIC). The treatment of the tested bacteria with the EOs of mango cultivars caused a steady loss in enterotoxins even when applied at the sub-MIC. Bacteria-inoculated apple juice treated with minimum bactericidal concentration of Alphonso oil was free from the bacteria after 5 days of incubation at 25 °C. Eighteeen volatile compounds were found to reduce the activity of the amylase enzyme and the most active was cedrelanol (-7.6 kcal mol-1) followed by alpha-eudesmol (-7.3 kcal mol-1) and humulene oxide (-7 kcal mol-1). The binding mode of both of cedrelanol and alpha-eudesmol with amylase enzyme was illustrated.

Characterization of Penicillium crustosum L-asparaginase and its acrylamide alleviation efficiency in roasted coffee beans at non-cytotoxic levels.

This work aims at isolating a fungal source for L-asparaginase production to be applied in reducing acrylamide levels in coffee beans at non-cytotoxic levels. An L-asparaginase-producing fungus was isolated from an agricultural soil sample and identified as Penicillium crustosum NMKA 511. A maximum L-asparaginase activity of 19.10 U/mL was obtained by the above-mentioned fungus when grown under optimum conditions (i.e. 16.96 g/L sucrose as carbon source, 1.92 g/L peptone as nitrogen source, pH 7.7 and 33.5 °C). Further, the produced L-asparaginase was purified and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) showed that P. crustosum L-asparaginase was a heterodimer enzyme with molecular weights of approximately 41.3 and 44.4 kDa. Also, the purified P. crustosum L-asparaginase was specific towards L-asparagine and showed negligible and no effects towards L-glutamine and D-asparagine, respectively. Additionally, the purified L-asparaginase reduced the acrylamide levels by 80.7% and 75.8% in light and dark roasted coffee beans, respectively. The amount of L-asparaginase used to reduce acrylamide was considered safe when cell viability reached 94.6%.