English abstract
Increased concern over the risks of synthetic plastic to environment has led to increased interest in
exploring eco-friendly plastic from renewable and natural waste resources including food waste.
Pomegranate peels are well known as a nutritive, antimicrobial and antioxidant rich byproduct.
This study spots the light to produce bioplastic (polyhydroxybutyrate) from pomegranate peel
waste as a novel substrate using Cupriavidus necator strain. This microbial strain tends to
accumulate polyhydroxybutyrate (PHB) intracellularly as an energy reserve. To make the
pomegranate peel as a suitable for microbial growth, the polyphenol content was extracted out.
The results showed that ethanol solvent was significantly (p<0.05) extracted more polyphenol
compared to hexane and water solvents. The pomegranate peel was subjected to chemical
pretreatment to increase the cellulose content and to reduce the lignin content. The peels were
pretreated using hydrochloric acid, sodium hydroxide and sodium peroxide. The highest cellulose
content of 41.625±0.00 and 49.5±0.00 obtained after sodium hydroxide and sodium peroxide
which was 20.25±0.001 before pretreatment. Enzyme hydrolysis was done using native fungus
Aspergillus foetidus isolated from pomegranate peels and also using pure cellulase enzyme. The
obtained hydrolysate of fungal cellulase used as substrate for PHB production using C. necator
through fermentation process. The hydrolysate containing reducing sugars (21 g/L) was inoculated
with 1% (v/v) inoculum of fresh activated PHB strain under optimized conditions (pH 7.0,
temperature 30°C and agitation 160 rpm). For PHB extraction, 10 ml of samples were collected at
regular interval (24h) to measure dry cell weight. The PHB extracted from dry biomass was
measured using GC-FID and UV-VIS spectrophotometer. C. necator produced maximum PHB
content of 56% at 72 h fermentation. Therefore, pomegranate fruit peels could be used as potential
alternative low-cost substrate to produce PHB.
