Kinetic parameters of Saccharomyces cerevisiae alcohols production using Nepenthes mirabilis pod digestive fluids-mixed Agro-waste hydrolysates

Abstract

In this study, microbial growth kinetics and modeling of alcohols production using Saccharomyces cerevisiae were evaluated using different hydrolysates in a single pot (batch) system. Mixed agro-waste hydrolysates from different pre-treatment methods, i.e., N. mirabilis/CP and HWP/DAP/CP, were used as the sole nutrient source in the fermentations used to produce the alcohols of interest. The maximum Saccharomyces cerevisiae concentration of 1.47 CFU/mL (×1010) was observed with HWP/DAP/CP hydrolysates, with a relative difference of 21.1% when compared to the N. mirabilis/CP cultures; the product yield based on biomass generation was relatively (20.2%) higher for the N. mirabilis/CP cultures. For the total residual phenolic compounds (TRPCs) generation, a relative difference (24.6%) between N. mirabilis/CP and HWP/DAP/CP pre-treatment systems was observed, suggesting that N. mirabilis/CP generates lower inhibition by-products. This was further evidenced by the lowest substrate utilization rate (3.3 × 10−4 g/(L·h)) for the N. mirabilis/CP cultures while achieving relatively similar product formation rates to those observed for the HWP/DAP/CP. A better correlation (R 2 = 0.94) was obtained when predicting substrate utilization for the N. mirabilis/CP cultures. Generally, the pre-treatment of mixed agro-waste using N. mirabilis/CP seemed appropriate for producing hydrolysates which Saccharomyces cerevisiae can effectively use for alcohol production in the biorefinery industry.