Travail de fin d'études en chimie et bio-industries : Isoamyl acetate production by non-conventional yeasts using agro-industrial by-products: bioprocess performance and Life cycle assessment.

Abstract

Isoamyl acetate is a volatile organic ester compound extensively utilised in food, beverages, personal care products, and fragrances owing to its distinctive banana or pear-like aroma. Conventional petrochemical synthesis does not meet the increasing consumer demand for natural or bio-based flavours for food and personal care applications. Microbial fermentation has emerged as an attractive alternative route for the sustainable production of bio-based isoamyl. However, the environmental sustainability of this process remains unquantified. In this study, ten non-Saccharomyces yeast strains from the genera Pichia, Kluyveromyces, and Meyerozyma were screened for isoamyl acetate production using isoamyl alcohol as the precursor. Pichia cactophila CAM-7-E produced the highest isoamyl acetate titre of 743.73 mg/L. The strain was then assayed for isoamyl alcohol toxicity at 2 g/L and 3 g/L in flask cultures with forced endive root (FER) juice. P. cactophila CAM-7-E grew in all conditions; biomass growth was slower with increasing isoamyl alcohol concentrations. Batch bioreactor fermentation at 30°C, 300-650 rpm, 0.25 vvm and at a pH of 5.0 with FER juice. A bubbling n-decane column was used as a trap to minimise any product loss by stripping. The strain metabolised fructose, glucose, and acetic acid, but showed a preferential consumption of acetic acid. Isoamyl acetate titres reached 19.59 mg/L after 24 h. A cradle-to-gate life cycle assessment was conducted to evaluate the sustainability of the microbial fermentation route, comparing two processes: a baseline based on bioreactor performance (BRT) using FER substrate and an alternative scenario (Scenario A) using rich glucose yeast-peptone medium. The ReCiPe2016 midpoint (H) method and a functional unit (FU) of 1 kg of isoamyl acetate in permeate at the gate of the pervaporation were used. The BRT condition had a higher environmental impact per FU than Scenario A. The pervaporation and bioreactor processes were the major hotspots, contributing over 40 % and 50 % of the total burden across most categories in BRT, respectively. This study demonstrates the potential applications of Pichia cactophila CAM-7-E for the biosynthesis of bio-based isoamyl acetate aroma. It provides a baseline study for life cycle assessment and sustainable process improvement within a circular bioeconomy framework.