Nepenthes mirabilis pitcher fluid functionality for agro-waste pre-treatment: effect of pH, temperature, trace element solution and the pore size of the waste

Abstract

Nepenthes mirabilis pitcher fluid is known to hydrolyse lignocellulosic mixed agro-waste (MAW) into fermentable sugars through a cocktail of oxidative and hydrolytic enzymes. However, the influence of factors such as pH, pore size, temperature and trace elements on its functionality is not adequately understood. This study aims to explore the potential of Nepenthes mirabilis pitcher fluid for the pre-treatment of MAW (>106 µm) by assessing the influence of the factors mentioned above on the yield of total reducible sugars (TRSs). The association between the trace element solution, pH, and temperature was evaluated using standard methods: Dinitrosalicylic acid (DNS) assay for the concentration of TRSs, and BET assay for the surface area and pore properties of the samples. The results showed that the highest concentration of TRSs (407.50 g/L) was at pH 2, albeit below ambient temperature, while pores (>106 µm) of agro-waste can accommodate <10 kDa enzymes, i.e., the enzymes could be adequately embedded within the pores of the milled agro-waste used. In conclusion, supplementing the pitcher fluids with a trace element solution did not improve the yield of TRS, but a low pH at below ambient temperature was more effective.