Abstract

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Rhizopus species from potato, millet and soil samples were isolated and screened for their ability to produce enzyme amylase. Potato and millet were dried, grinded and the samples including soil were serially diluted and spread plated (0.1ml) on sterile potato dextrose agar (PDA) platesincubated at 35°C for 5days. Colonies were repetitively sub-cultured in order for pure cultures. Fungi Rhizopus was macroscopically and microscopically identified based on standard procedures. Rhizopus species were screened using agar plate method at which hydrolysis zones were observed and measured in millimeter (mm) by meter rule. Enzyme was quantified by solid state fermentation (SSF) during which wheat bran (the substrate/medium) and time (96hrs) was used for production. For enzyme extraction, the mixture of fermented medium and tween 80 (0.1%) was shaken by rotary shaker, squeezed by muslin cloth and filtered through filter paper (Whatman No. 1). For enzyme activity determination; crude extract of enzyme was mixed with starch, Sodium Chloride (NaCl) and phosphate buffer and the mixture was incubated in a water bath for 30mins at 40°C, DNSA was added to stop the reaction, heating the mixture again for 5mins after which distilled water was added and the absorbance 540nm was taken using spectrophotometer. About three (3) Rhizopus species were isolated from millet including R. microsporus, R. nigricans, and Rhizopus specie with zone of hydrolysis 31.0, 28.6 and 28.2mm and their enzyme activity 76, 52 and 48% respectively. Subsequently, only four (4) Rhizopus species were isolated from soil.They includeR. oryzae, R. americanus, R. oligosporus and R.nigricans with hydrolysis zone 27.4, 25.3, 25.0, 22.0mm in diameter and enzyme activity 50, 45, 46 and 36% respectively.Similarly, about three (3) Rhizopus species were isolated from potato.They includeR. oligosporus, and two (2) Rhizopus species with zone of hydrolysis 22.8, 20.7, 19.5mm and enzyme activity 40, 38 and 29% respectively. This reveals fungi Rhizopus can be isolated from varied raw food sources and soil with strain R. microspores isolated from millet having greater potential of producing this amylase enzyme

Keywords: Rhizopus, Screening, amylase and Production