Encapsulation in ZIF-8 as a Biopreservation Strategy and Enhancement of Thermal Tolerance of Saccharomyces cerevisiae

This study evaluated ZIF-8 as an immobilization matrix for Saccharomyces cerevisiae CAT-1 to determine its effectiveness as a biopreservation strategy for enhancing robustness and performance in ethanol fermentation under thermal and chemical stress. Encapsulated and free cells were compared in sequential batch fermentations to assess operational stability and reusability. Thermal tolerance assays were conducted in YPD medium at 25–50°C, and protective performance was further examined under inhibitory conditions representative of lignocellulosic hydrolysates derived from passion fruit peel. Biomass formation, cell viability, glucose consumption, substrate-to-product conversion yield, volumetric productivity, and fermentation efficiency were evaluated. ZIF-8 encapsulation significantly enhanced thermotolerance and resistance to inhibitory compounds. Encapsulated cells maintained consistently higher viability across the tested temperature range, reaching 96.7% at 50°C compared to 82.9% for free cells. Within the mesophilic range (25–35°C), immobilized cultures demonstrated superior fermentative performance, achieving fermentation efficiency above 93% at 30°C, whereas free cells reached 78.86%. Under hydrolysate stress, encapsulated cells preserved 99.42% viability after 48 h and retained metabolic activity in a subsequent fermentation cycle. Overall, ZIF-8 immobilization improved cellular stability and process resilience, supporting its application in intensified, inhibitor-rich bioprocesses for industrial ethanol production.