Utilization of palm oil-based by-products and waste as feedstock for polyhydroxyalkanoate biosynthesis
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Date
2009-12
Authors
Kek, Yik Kang
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Abstract
The utilization of by-products and wastes from the palm oil industry is aimed to
reduce the overall production cost of polyhydroxyalkanoate (PHA). In this study, palm
oil refining by-products; palm acid oil (P AO), palm kernel acid oil (PKAO), palm fatty
acid distillate (PF AD), and palm oil-based used cooking oil (UCO) were evaluated as
the carbon substrate for poly(3-hydroxybutyrate) [P(3HB)] and poly(3-
hydroxybutyrate-co-3-hydroxyhexanoate) [P(3 HB-co-3 HHx)] synthesis using
Cupriavidus necator H16 and its transformant. Important cultural parameters that
significantly affected the cell biomass and P(3HB) synthesis of C. necator H16 grown
on 5 giL PKAO were identified. An initial urea concentration of 4 mM (CIN ratio-38)
gave the highest DCW and total P(3HB); 5.4 and 3.2 giL respectively. Elevation of
culture volume from 50 to 100 mL (in 250 mL flask) further enhanced the P(3HB)
production up to 77 wt% of DCW, whereby P(3HB) concentration of 4.1 gIL was
obtained from 5 gIL PKAO. For the bioconversion of UCO to P(3HB) by C. necator
H16, the most suitable nitrogen and carbon source concentration for cell growth and
P(3HB) synthesis were determined. A total of 18 mM urea and 20.0 giL DCO (CIN-30)
contributed to the highest DeW (25.4 giL) and intracellular P(3HB) content (71 wt%),
which resulted in P(3HB) concentration of 18 giL. On the other hand, P(3HB-co-3HHx)
copolymer was synthesized when the transformant of C. necator mutant was grown on
PAO, PKAO, PF AD or DeO as the sole carbon source. With an approximate P(3HBco-
3HHx) content of 50 wt«>1o, a higher DCW could be obtained from UCO; 5 gIL than
those obtained from PKAO; 3.8 giL. In addition, manipUlation of the initial carbon
source concentration was found to improve significantly the P(3HB-co-3HHx) yield
from the wasteslby-products. At the initial P AOIPKAOIPF AD concentration of 9 gIL,
the highest DeW and copolymer content were 5.7 giL and 70 wt% respectively at 72 h
of cultivation. In the case of using UCO as the carbon source, an initial concentration of
10 gIL contributed to 8.4 and 5.6 giL of DeW and P(3HB-co-3HHx) concentration
respectively and the corresponding copolymer content in the biomass was 67 wt%.
Time profiles of C. necator transformant grown on 10 giL ueo and 15 mM urea
showed a constant 3HHx monomer fraction of 3 - 5 mol% within 96 h of cultivation.
This study has demonstrated that the surplus palm oil-based wastes/by-products are
potential carbon source for the production ofPHA.
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Keywords
Wastes from the palm oil industry is aimed to , reduce the overall production cost of polyhydroxyalkanoate