| dc.description.abstract | The gut of insects is the natural habitat of various microbes that have the ability to
degrade cellulose, which is the main component of plant walls. Oryctes rhinoceros L.,
is one of the pests in oil palm and is thought to have potential cellulolytic bacteria and
fungi in the digestive tract that have not been widely explored. This study aims to
uncover the diversity and potential of cellulolytic bacteria and fungi from the gut of
O. rhinoceros L. as a new source of enzymes. Isolation of bacteria and fungi is
conducted by the spread plate method using the medium of Nutrient Agar (NA) for
bacteria and Potato Dextrose Agar (PDA) for fungi. Screening of cellulolytic activity
was conducted using the selective medium of Carboxymethyl Cellulose (CMC) 1%.
Identification of isolates could potentially be conducted based on morphological
characters as well as molecular analysis of the 16S rRNA gene for bacteria and ITSrDNA for fungi. The cellulase enzyme was purified using gel filtration
chromatography and ion exchange chromatography using DEAE-cellulose. Enzyme
characterization includes molecular weight analysis with SDS-PAGE, measurement of
specific activity, pH, optimal temperature, and the influence of metal ions on enzyme
activity. A total of 42 bacterial and fungal isolates were successfully isolated from the
digestive tract of instar III larvae and O. rhinoceros L. beetles, consisting of 19
bacterial isolates and 23 fungal isolates. Based on the Shannon and Simpson index, it
shows that the diversity of bacteria and fungi in the gut of O. rhinoceros L. is high
with a Shannon index value of 1.768-1.979 and a Simpson index of 0.826-0.847. Four
isolates showing the highest cellulolytic activity index were identified as Bacillus
tequilensis B01L (1.28) and Fusarium oxysporum F05L (0.90) isolated from the
gastrointestinal tract of instar III larvae. Bacillus cereus B19L (2.50) and Aspergillus
niger KOr15J (1.93) from the digestive tract of beetles. Pure cellulase yields a
molecular weight of 52.23 kDa for bacterial enzymes and 72.61 kDa for fungal
enzymes obtained from ion exchange chromatography. The highest specific activity
was shown by the cellulase enzyme of B. cereus B19L at 9.221 U/mg, followed by B.
tequilensis B01L (8.529 U/mg), F. oxysporum F05L (8.077 U/mg), and A. niger
KOr15J (4.242 U/mg). The cellulase activity of the bacteria shows optimum at pH 6–
7 and pH 5–6 for fungi, an optimum temperature of 30°C to 60°C. Ca²⁺ ions increase
the activity of cellulase enzymes from bacteria, while Fe²⁺ ions increase cellulase
activity from fungi. This study shows that bacteria and fungi from the digestive tract
of O. rhinoceros L. have high diversity and great potential in the stable and efficient
production of cellulase enzymes. This potential also shows the alpha ability to degrade
filterpaper, making it very prospective for the bioconversion of cellulose waste. | |
