Process integration for efficient conversion of cassava peel waste into polyhydroxyalkanoates

Polyhydroxyalkanoates (PHA) are biodegradable polyesters that can be produced from renewable resources. However, PHA biomanufacturing is costly compared to petrochemical -based plastics. A promising solution consists of using cassava (Manhiot esculenta) waste, abundant biomass in developing countries, as a carbon source for PHA production. This study involved characterising untreated and acid -hydrolysed cassava peel (CP) to confirm the degradation of polysaccharides into fermentable sugars after pre-treatment. A chemical and biological integrated process was developed, optimising the pre-treatment using a central composite design. The highest conversion of CP into reducing sugars was 97% (w/w) using 3 M H2SO4, 120 min and 90 oC. The ability of Cupriavidus necator to grow on CP hydrolysate and produce PHA was screened resulting in up to OD600 15.8 and 1.5 g/L of PHA (31% (gPHA/gDCW)). Flow cytometry allowed rapid, simple, and high -throughput assessment of PHA content. These findings pave the way for developing a biorefinery platform for PHA production from cassava waste.