Abstract:
Microbial proteases are hydrolytic enzymes that are widely used in many industrial
processes. This study aimed to evaluate the production of alkaline protease (AP) from
fungal isolates sourced from avocado (Persea americana Mill.) peel (AVP) and avocado
seed (AS) under solid state fermentation (SSF). AVP and AS was collocated form Harar
juice house into plastic bag and serial diltuion method was used for fungal isolatin. The
isolates were subutured on potato dextrose agar (PDA) and AP production was assessed
by measuring enzyme activity in the crude enzyme using the spectrophotometric method.
A total of five fungal isolates were isolated and identified based on their morphological
characterization to the genus level. Skim-milk agar media was used to test fungal isolates
for their ability to produce AP. The optimal SSF parameters (pH, temperature,
incubation time, and carbon and nitrogen sources) were determined using the one FIctor-at-a-time method. Data were analyzed using SPSS, and statistically significant
differences were considered at P<0.05. The result revealed that all five isolates were
able to produce AP and the first four isolates (Aspergillus, Fusarium, Rhizopus, and
Saccharomyces) were selected for further study based on clear zone diameter formed
aroud the colonies. The optimal temperature for AP production was 30°C, with enzyme
activities of 87.68 U/ml and 60.77 U/ml for Aspergillus and Saccharomyces.respectively.
The maximum enzyme yield was obtained at pH 9.0 for Aspergillus and Fusarium, and
75.525 U/ml for Rhizopus. Relatively, the preferred carbon source was wheat flour, while
peptone and yeast extract were relatively good nitrogen sources for AP production. It
can be concluded that fungal isolates such as Aspergillus and Rhizopus from AVP and
AS were promising candidates in alkaline protease production which is required by
different industrial applications. Hence, further molecular identification and
characterization of the screened fungal isolates should be conducted to identify them at
the species level. The alkaline protease from each isolate should be purified using
different methods to increase the enzyme activity.
