Screening of potential antibiotic action of cellulolytic fungi

Twenty different strains of filamentous fungi were initially selected for evaluation of cellulolytic activity using a single test in a simple mineral salts culture medium with filter paper as the only carbon source. Those fungi strains that were capable of completely breaking the filter paper strip within 4–8 d were assayed also for antimicrobial action, using Staphyloccocus a ureus ATCC 6538P according to the so-called agar piece method. We screened three different strains with both capacities: the production of cellulolytic activity and antibiotic action. The experimental results suggest that the fungi Pinicillium sp. FOPCO1, Aspergillus sp. F0Q001, and Cephalosporium sp. F03800 have both capabilities because they grew rapidly on cellulose as the only carbon source and were able to produce an area of growth inhibition in S. aureus of approx 2.04, 1.57, and 2.39 cm, respectively, on agar plates using the agar piece method. Subsequently, the antibiotic production obtained with those cellulolytic strains was evaluated by submerged fermentation at the flask level, in a simple culture medium containing lactose without biosynthesis precursor, obtaining 3670, 2830, and 4060 antibiotic units/mL, referred to as penicillin G, whereas for cellulolytic activity, the results were 1.34, 1.81 and 0.57 FPU/mL, respectively.     

α-amylase production by free and immobilized Bacillus subtilis

The effect of glucose on the α-amylase production by Bacillus subtilis ATCC-21556 was studied. Initial glucose concentrations up to 20 g/L were found to be directly proportional to the specific α-amylase production in an immobilized-cell batch system, whereas a free-cell batch system presented an inversely proportional relationship with the initial glucose concentration. This might be owing to the α-amylase repression by the glucose present in the culture medium. Three hundred eighty-five percent of the specific α-amylase production with the free-cell system was produced by the immobilized-cell batch culture.