An integrated approach for pineapple waste valorisation. Bioethanol production and bromelain extraction from pineapple residues

Abstract

Waste management is critical for the food industry for which there is increasing interest in food waste valorisation processes. Pineapple waste, an abundant agro-industrial residue, is studied as a low-cost material for the generation of different value-added products. The work succeeds in obtaining bioethanol and proteolytic enzymes from these residues and, accordingly, integrated approaches for pineapple waste valorisation combining the production of bioethanol and bromelain in a unique process are suggested. There are several potential uses for the products obtained, while bioethanol is a well-known alternative to petroleum-based transport fuels, bromelain is mainly used in the food and pharmaceutical industries, and it has also applications in the cosmetics, textile, leather and detergents ones. Proposals are based on the optimization of bioethanol production through different fermentation and saccharification processes: direct fermentation of the liquor, consecutive saccharification and fermentation of the solid waste and simultaneous saccharification and fermentation of the solid waste. Simultaneous saccharification and fermentation increased ethanol production (5.4 ± 0.1% v/v) as compared to direct fermentation (4.7 ± 0.3%) and saccharification and fermentation of the solid waste (4.9 ± 0.4% v/v) processes. On the other hand, bromelain separation was accomplished using membrane separation techniques (microfiltration and ultrafiltration), and further stabilization of the concentrated stream by freeze-drying. An increased protein concentration after downstream processes was confirmed by the Lowry analytical method (11.5 ± 1.2 to 21.0 ± 1.3 mg/mL in the retentate), and the proteolytic activity of the lyophilized powder was estimated in 340–805 Gelatine Digestion Units. The resulting permeate successfully underwent fermentation for bioethanol production.