Food & Nutrition

Arab Journal of Food & Nutrition
59. A Study to Produce Fungal Rennin-like Enzyme and Its Use in the
Manufacturing of Nabulsi Cheese (2002)
Zaki Ali Hassan Tubesha\ University of Jordan
Supervisor:Dr. Khalaf S. Al-Delaimy
This study aimed to isolate and characterize a mold from the environment able to
produce rennin-like enzyme, and its possible applications in Nabulsi cheese
manufacture. Among the molds isolated from sixty one samples of soil and animal
secretions, twenty isolates were found to have morphological, microscopical, and
cultural characteristics Mucor, and all were able to produce rennet enzyme activities.
Among the twenty Mucor isolates, Mucor (M.Z.20) was found to produce the highest
rennet enzyme activity, and hence adopted thereafter in this study. Thirty degree
centigrade was found to be the optimum temperature for both the growth and spore
formation on potato dextrose agar and also optimum for rennin-like enzyme excretion
on fortified wheat bran media mixture during three and four days respectively. Clay
pots were found to be the most favorable containers for enzyme production compared
with Erlenmyer flasks or plastic pots (140% and 325%) respectively. The Log. 2 and
log. 3 per gram of fermentation media was the optimun inoculum concentration after
four days incubation period using clay pots for the highest production of rennet
enzyme (597 RU) produced by Mucor (M.Z.20) under similar experimental condition.
Much lower values if using erlnmeyer flasks. Extending incubation time to five days
caused a drastic decrease in rennet production. The highest rennet activity was
produced in the fermentation media mixture containing wheat bran and lentil straw
(1:1 w/w) using whey as a moisting liquid (185 RU), then slightly lower values when
using any of salt solution, or distilled water. Followed by wheat bran alone, then
mixture of wheat bran and wheat straw (1:1). Activity of Mucor (M.Z.20) rennet
extract was stable (100%) at 30°C for 30 min at both pH 3.5 and 4. Lower or higher
pH levels caused a decrease in the activity reaching its minimum (1%) at pH 8. At
60°C for 10min the enzyme activity practically lost its activity at all pH levels except
at pH 3.5 (2.1%), pH 4 (4%), and pH 4.5 (2.3%). At pH 4 using different storage
temperatures it was found that the enzyme retained its complete activity (100%) after
six weeks at 5°C and 10°C and after three and two weeks at 20°C and 30°C
respectively. The crude extract of renninlike fungal enzyme was successfully applied
for white and Nabulsi cheese. A panel of 10 persons found generally an acceptability
of the Nabulsi cheese processed by both, the crude rennet extract of this study and that
of using commercial rennin-like enzyme.
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