Comparative study of chemical and enzymatic pre-treatments of Kitchen waste (KW) to generate fermentable sugars for the production of polyhydroxyalkanoates (PHA)

Kitchen waste (KW) production is anticipated to rise because of accelerated urban and economic growth, particularly in Asian nations. Therefore, applications/recycling of KW should be explored for its effective utilization to generate a sustainable source of energy that will ultimately avoid massive economic and energy losses. The main goal of this study was to investigate the combinational effect of thermochemical and enzymatic pre-treatment on synthetic KW to enhance the release of fermentable sugars for the synthesis of value-added products such as polyhydroxyalkanoates (PHAs). The thermochemical pre-treatment of KW samples was performed using 4 N HCl, 4 N H₂SO₄, and 4 N NaOH at a concentration of 0–30% (v/v), 30–100 °C for 0–120 min. Furthermore, to enhance the total fermentable sugars, variable enzyme dosages were added after acidic or alkaline pre-treatments (0–1% v/v α-amylase and 0–1% v/v amyloglucosidase-AMG) while maintaining a constant pH 5, temperature 50 °C, and time 30 min. Pre-treatment of KW with acid (15% v/v 4 N HCl in water) at temperature 100 °C, followed by enzymatic hydrolysis, i.e., 0.6% (v/v) α-amylase and 0.4% (v/v) amyloglucosidase (at pH 5, 50 ⁰C and 60 min) resulted in the maximum concentration of fermentable reducing sugars (46.13 g/L) in the hydrolysate.