Study on Isolation of Rice Bran Lipase and its Hydrolysis Reaction.

Rice bran contains an endogenous lipase, which
degrades the oil present in it to free fatty acids and
glycerol. The purpose of the study was to find out the
effect of individual parameters such as moisture
content, temperature, incubation period, defatted rice
bran/crude lipase extract and substrate concentration
on the activity of lipase enzyme in vitro. Rice bran
was defatted by using three different kinds of solvents
by two methods, one at room temperature and another
at 5-8°C using Soxhlet extraction method. The resultant
defatted rice bran had moisture, 7.7-8.2%; residual
fat, 2.2-3.2%; water solubles, 16.2-21.7%; water
insolubles, 78.2-83.7%; and protein content, 8.2-9.0%.
The LAU/g protein/h was slightly more in Soxhlet
defatted bran (1270) than in the room temperature
extracted bran (1032). Buffer (pH 7.0 with CaCl2
solution) was used for the extraction of crude lipase
from defatted rice bran. The yield of dry extract from
Soxhlet defatted rice bran was a little more (10 g/
100g with 1578 LAU/g/h units) while it was slightly
lesser for room temperature defatted bran (7.1g/100g
with LAU of 525 units). The hydrolysis reaction of
defatted rice bran and the crude enzyme extract
increased with increase in moisture content, crude
enzyme concentration and the incubation period and
the reaction slowed down with increase in temperature
and substrate concentration. This was probably due
to inactivation of the enzyme at higher temperatures
and decreased amount of the enzyme concentration
respectively. The optimum conditions for carrying out
the hydrolysis reaction for defatted bran and its crude
enzyme extract were moisture content (0.5mL/2.0
mL), temperature (30°C), incubation period (72 h),
lipase concentration (defatted bran, 0.5 g; crude
enzyme extract 0.1 g) and substrate concentration
(0.2 g). During the normal process of oil, extraction
from rice bran the enzyme gets deactivated and
hence its extraction from commercial deoiled bran is
not possible. This study throws light on extraction and
utilization of the enzyme using Soxhlet method of
defatting.