Effects of glucose as carbon catabolite repressor on alpha-amylase and glucoamylase production in Indonesian indigenous fungi

Aims@#The study aimed to investigate the effect of glucose on alpha-amylase and glucoamylase production in some Indonesian indigenous fungi.@*Methodology and results@#Fungi were screened for their ability to produce alpha-amylase and glucoamylase in the presence of glucose. The strains were grown in a medium containing starch and glucose as carbon sources with glucose concentrations varying from 0 to 5% for four days, and the alpha-amylase and glucoamylase were analyzed at the end of the growth period. Most strains showed repression on the amylases production when glucose was added to the medium. However, some strains showed no repression on amylases production when glucose was supplemented to the medium. The addition of glucose repressed glucoamylase production, but no repression on alpha-amylase was noted for strain KKB4, vice versa, there was repression on alpha-amylase production but no repression on glucoamylase production for strain FIG1. Strains FNCC 6151 and MLT1J1 showed no repression on both alpha-amylase and glucoamylase production when glucose was added to the medium up to 5%. The occurrence of repression in the production of alpha-amylase and glucoamylase was strain-specific.@*Conclusion, significance and impact of study@#Out of the nine indigenous fungi strains examined, strains FNCC 6151 and MLT1J1 showed no repression on both alpha-amylase and glucoamylase production when glucose was added to the medium up to 5%. Those two strains have the potential to be improved further to produce both alpha-amylase and glucoamylase.

Diversity and functional characterization of antifungal-producing Streptomyces-like microbes isolated from the rhizosphere of cajuput plants (Melaleuca leucodendron L.)

Aims@#The study was undertaken to evaluate the diversity of actinomycetes from the rhizosphere of the cajuput plant (Melaleuca leucodendron L.) using ARDRA, and to examine their in vitro antifungal potency against selected fungi. @*Methodology and results@#A total of 78 Streptomyces-like microbes were isolated from the limestone rhizosphere of cajuput plants and cultured in SN agar medium. The ability to inhibit fungal growth was observed using a dual culture assay. The diversity of the isolates was examined by morphological and genotype profiling using ARDRA (Amplified 16S ribosomal DNA restriction analysis), following which they were assigned to eight groups. Seventeen (21.8%) strains showed the ability to produce the antifungal compound as evidenced by their antagonism in vitro against the tested fungi, namely Saccharomyces cerevisiae BY 47420, Candida albicans CGMCC 2538, Aspergillus flavus NRLL 3357, and Fusarium oxysporum KFCC 11363P in the dual culture assay. One isolate, GMR22, which showed potent antagonism against unicellular and filamentous fungi, displayed 97% 16S rRNA sequence similarity to Streptomyces vayuensis. @*Conclusion, significance and impact of study@#This study demonstrated that a diversity of Streptomyces-like antifungal producing microbes were present in the rhizosphere of cajuput plants in the Wanagama Forests of Indonesia. This rhizosphere represents a potential new source of actinomycetes that produce biologically active compounds. One selected strain (GMR22) has the potential to be developed as a commercial biofungicide.