Bioconversion Of Old Oil-Palm Trunk Residues Via Enzymatic Hydrolysis By Penicillium Rolfsii C3-2(1) LBRL Using Reducing Sugars As An Indicator
Loading...
Date
2015-04
Authors
Kok Chang, Lee
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
Due to the decreased oil productivity of old oil-palm trees after 25 years, large
quantities of trunks as the waste were generated from the replanting activities. The
felled old oil-palm trunk was found containing large quantity of sap with high
concentration of sugar contents. The oil-palm trunk residues which are the residual
substances after squeezing sap will be discharged in large quantity. These oil-palm
trunk residues in the form of agro-industrial waste constitute a potentially enormous
source of feedstock for bioconversion into biofuel, and other value-added chemicals
without competition with food sources. A filamentous fungus namely c3-2(1) was
screened and selected for its strong activities against oil-palm trunk residues. Fungal
isolate c3-2(1) was identified as Penicillium rolfsii by morphological characterization,
microscopical observations and confirmed by molecular identification. It was
designated as Penicillium rolfsii c3-2(1) IBRL. Oil-palm trunk residues-hydrolyzing
specific activity of the culture supernatant from P. rolfsii c3-2(1) IBRL was found
superior to those of commercial enzymes Celluclast 1.5L (Sigma) and Accellerase
1500 (Genencor) which exhibited 2 to 3-fold and 3 to 4-fold higher activity,
relatively. On the other hand, P. rolfsii c3-2(1) IBRL exhibited a greater xylan,
arabinan and laminarin-hydrolyzing activities than those commercial enzymes. The
optimal conditions for oil-palm residues hydrolysis was found at pH 5.0 and
temperature of 50°C, with higher thermal-stability of crude enzymes. After 48–72 h
of biomass saccharification, 1 to 1.5-fold higher total sugar conversion was
performed by enzyme of P. rolfsii c3-2(1) IBRL compared to commercial enzymes.
Maximum total sugar conversion yield of approximately 56% was obtained from
enzymatic hydrolysis on oil-palm trunk residues by crude enzyme of P. rolfsii c3-
2(1) IBRL compared to total sugar conversion yield 43% from Celluclast 1.5L and
40% from Accellerase 1500 when 14 FPU/g substrate of enzyme loading added at 48
h reaction. The isolated lignin residual from oil-palm trunk residues affected the
biomass hydrolysis, which revealed that P. rolfsii c3-2(1) IBRL is capable to produce
weak ‘lignin-binding’ enzymes which might contribute to the higher efficiency
hydrolysis on oil-palm residues. Purification of xylanase and laminarinase were
successfully achieved from P. rolfsii c3-2(1) IBRL. The xylanase had the following
physical and chemical properties: substrate specificity on xylan from birchwood,
Vmax=691.6 μmol/min/mg and Km=5.72 mg/ml; optimum pH, 5.0; optimum
temperature, 50°C; temperature stability after the treatment at 50°C for 4 hr (residual
activity > 90%); molecular weight by SDS-PAGE analysis, about 35 kDa. The
laminarinase was tested on laminarin from Laminaria digitata as substrate in which
Vmax=372.2 μmol/min/mg and Km=0.0817 mg/ml; optimum pH, 5.0; optimum
temperature, 70°C; temperature stability after the treatment at ≤ 55°C for 4 hr
(residual activity > 90%); molecular weight by SDS-PAGE analysis, about 75 kDa.
Considerable increasing synergism effect was observed on added purified xylanase
with commercial enzymes during saccharification of oil-palm residues based on total
sugar conversion, suggesting it is one of the key enzymes for the hydrolysis of oilpalm
trunk residues.
Description
Keywords
Oil-Palm , Penicillium Rolfsii C3-2(1) LBRL