Application of Biorefinery Concept to the Production of Bromelain, Ethanol, and Xylitol from Pineapple Plant Waste

Abstract

The massive potential of pineapple fruit production can produce a sizable amount of waste, around 75% (w/w) of pineapple weight, contributing to global environmental problems. For this reason, biorefinery techniques are urgently needed to convert pineapple plantation waste into high-value-added bioproducts including bromelain, various sugars, xylooligoscharide, xylitol, and ethanol. The purpose of this study was to examine the effectiveness of converting pineapple plantation waste into bromelain, xylitol, and ethanol. In this study, the activity of the bromelain enzyme was tested in each part of the pineapple plant waste. The configuration of the hydrolysis and fermentation processes used to make ethanol and xylitol from the rest of the pineapple plant waste from bromelain extraction was also investigated. Bromelain is a proteolytic enzyme found in pineapple plants and can be isolated from every part of pineapple plant waste. Enzyme activity under several conditions, such as crude extract, pure extract, and dried extract, has been studied to determine the best conditions for the downstream process of this enzyme’s production in the future. The purification of bromelain involved the utilization of the precipitation method followed by dialysis, whereas the drying process of bromelain employed the freeze-drying method. The bromelain enzyme specific activity is shown to be highest in the pineapple stem, as observed in crude-extract (1.45 ± 0.06 CDU/mg), purified-extract (10.38 ± 0.06 CDU/mg), and dried-extract (12.05 ± 0.43 CDU/mg) conditions. Using the pineapple stem to extract bromelain can produce lignocellulosic waste, which is made up of 39.47% starch, 19.96% hemicellulose, 36.44% cellulose, and 6.05% lignin. The high content of starch, cellulose, and hemicellulose has the potential to be used as feedstock for ethanol and xylitol fermentation. In this study, ethanol and xylitol fermentation were carried out using two methods: separate hydrolysis and fermentation methods (SHF) and semi-simultaneous saccharification and fermentation methods (semi-SSF). As a result, fermentation using the semi-SSF method produced ethanol with a higher titer and yield (22.12 ± 0.05 g/L and 0.44 ± 0.00 g/g, respectively). However, the production of xylitol was found to be insignificant, regardless of whether it was obtained using SHF or semi-SSF. The purification of bromelain involved the utilization of the precipitation method followed by dialysis, whereas the drying process of bromelain employed the freeze-drying method.