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Enhanced production of polygalacturonase in solid-state fermentation: selection of the process conditions, isolation and partial characterization of the enzyme

100%

Zaslona H., Trusek-Holownia A.

issue 4

651-657

Polygalacturonase (PG) production by Penicillium chrysogenum during solid-state fermentation was accompanied by decomposition of orange peels. A leaching procedure was developed through the selection of solvent, time and intensity of stirring. A maximum PG activity was observed after 48 h peel inoculation. Further cultivation decreased the enzyme activity significantly, up to 60% of the maximum PG activity. During fermentation, a rapid acidification of the solid medium which inhibited the pectinolytic enzyme, was observed. Buffering agents with different pH values and different ionic strengths were examined to identify the most suitable medium to avoid this problem. Buffer addition counteracted acidification and enhanced active protein production, which was observed for all of the applied pH values (6.5-8.0) of the buffering agent. The most satisfactory results were obtained when using the highest pH at 8.0. The protein content and PG activity increased from 3.5 mg/g and 1.09 U/g to 7.7 mg/g and 7.11 U/g during cultivation, with uncontrolled and pH-controlled medium, respectively. Measurements at wide pH and temperature ranges indicated an optimum for PG activity at pH 5.0 and 43°C; however, high thermal stability corresponded to lower temperatures, and a temperature of 37°C is thus recommended. Under these conditions, the operational stability was determined to be t1/2=570 h.

Antifungal activities of moulds associated with selected stored grains and legumes

84%

Ohabughiro N. B.

World News of Natural Sciences

2023

vol. 50

52-59

An antifungal agent can either kill or inhibit the growth of fungi by interfering with the formation of fungal cell membrane, weakening it and hindering cell division. Antifungal agents of amphotericin B, ketoconazole, fluconazole and voriconazole of Thermo Fisher Scientific limited were used for this study. Cultural analysis of stored grains and legumes (rice, maize, wheat, groundnut and beans) from Imo State was done using streak plate method. Sabouraud dextrose agar was used for the culture while Mueller Hinton agar was used for Antifungal sensitivity test. Moulds were further identified using 18s rRNA gene sequencing method. The antifungal sensitivity profile of isolated and identified moulds was evaluated using the clinical laboratory and standard institute approved methods for testing of moulds, the disk diffusion and tetrazolium chloride test. The results showed that Aspergillus flavus, Aspergillus tamarii, Aspergillus niger, Aspergillus brunneoviolaceus and Penicillium chrysogenum were the moulds isolated and identified using both cultural and 18S rRNA sequence. The fungal isolates were susceptible to ketoconazole and voriconazole. Amphotericin B was both resistant and susceptible to different moulds. The fungal isolates were resistant to fluconazole. Inhibition effects were more with the antifungal disc than with tetrazolium salts. All the isolates were resistant to tetrazolium chloride and gave no zone of inhibition. Combination of antifungal agent and tetrazolium chloride showed sensitivity only to ketoconazole. Antifungal disc alone gave a better zone of inhibition than the combination of antifungal agents with tetrazolium salts. This study showed that ketoconazole has greater inhibitory potential than other antifungal agents. Ketoconazole remains the best drug of choice among the studied antifungal agents for fungal infections. Therefore antifungal drugs can be used against moulds of economic importance in the country.

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1 Acta Biochimica Polonica

1 World News of Natural Sciences

1 2023

1 2015

1 Ohabughiro N. B.

1 Trusek-Holownia A.

1 Zaslona H.

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Enhanced production of polygalacturonase in solid-state fermentation: selection of the process conditions, isolation and partial characterization of the enzyme

Antifungal activities of moulds associated with selected stored grains and legumes