Aim
This work was conducted to produce, purify and characterize biosurfactants from Aspergillus flavus AF612 isolated from citrus fruit.
Methods and results
Biosurfactant named ‘Uzmaq’ was isolated from A. flavus AF612. The chemical characterization of the biosurfactant was conducted. Biosurfactant Uzmaq produced by A. flavus, was composed of methoxy phenyl oxime glycosides. Two molecular forms of the biosurfactant, Uzmaq‐A and Uzmaq‐B were isolated. Biological properties (antifungal activity) were evaluated. The fractions of the biosurfactant were isolated and their surface properties were analysed. Uzmaq‐A and Uzmaq‐B had critical micelle concentration (CMC) around 170 and 80 mg l−1, and lowered surface tension of water up to 20 and 25 m Nm−1 respectively. The biosurfactants were stable at pH 3–12 and temperature up to 80°C. Growth and biosurfactant production kinetics were also analysed.
Conclusion
Novel biosurfactant Uzmaq was produced from A. flavus, which was composed of methoxy phenyl oxime glycosides. The surface activity of Uzmaq was better than the maximum values of synthetic chemical surfactants. The biosurfactant showed antifungal activity and self‐assembling properties.
Significance and Impact of the Study
Aspergillus flavus AF612 can be used for commercial production of Uzmaq that may be employed for controlled drug release applications and bioremediation.
Invertase (b-D-fructofuranoside fructohydrolase, EC 3.2.1.26) finds major uses in confectionery and in the production of invert syrup. In the present study, we report on invertase production by wild cultures of Saccharomyces cerevisiae. The yeast strains were isolated from dates available in a local market. Five hyperproducing yeast strains (>100-fold higher invertase activity) were kinetically analysed for invertase production. Saccharomyces cerevisiae strain GCA-II was found to be a better invertase-yielding strain than all the other isolates. The values of Q p and Y p/s for GCA-II were economical as compared to other Saccharomyces cultures. The effect of sucrose concentration, rate of invertase synthesis, initial pH of fermentation medium and different organic nitrogen sources on the production of invertase under submerged culture conditions was investigated. Optimum concentrations of sucrose, urea and pH were 3, 0.2 (w/v), and 6 respectively. The increase in the enzyme yield obtained after optimization of the cultural conditions was 47.7%.
The present study describes the predicted model and functional characterization of an endochitinase (30 kDa) from corms of Gladiolus grandiflorus. ESI‐QTOF‐MS generated peptide showed 96% sequence homology with family 18, Class III acidic endochitinase of Gladiolus gandavensis. Purified G. grandiflorus chitinase (GgChi) hydrolyzed 4‐methylumbelliferyl β‐d‐N,N′,N′′‐triacetylchitotriose substrate showing specific endochitinase activity. Since no structural details of GgChi were available in the Protein Data Bank (PDB), a homology model was predicted using the coordinate information of Crocus vernus chitinase (PDB ID: 3SIM). Ramachandran plot indicated 84.5% in most favored region, 14.8% in additional and 0.6% in generously allowed region while no residue in disallowed region. The predicted structure indicated a highly conserved (β/α)8 (TIM barrel) structure similar to the family 18, class III chitinases. The GgChi also showed sequence and structural homologies with other active chitinases. The GgChi (50 μg/disc) showed no antibacterial activity, but did provide mild growth inhibition of phytopathogenic fungus Fusarium oxysporum at a concentration of 500 μg/well Similarly, insect toxicity bioassays of GgChi (50 μg) against nymphs of Bemisia tabaci showed 14% reduction in adult emergence and 14% increase in mortality rate in comparison to control values. The GgChi (1.5 mg) protein showed significant reduction in a population of flour beetle (Tribolium castaneum) after 35 days, but lower reactivity against rice weevil (Sitophilus oryzae). The results of this study provide detai.led insight on functional characterization of a family 18 class III acidic plant endochitinase.
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