Theoretical Basis and Empirical Validation of a Fermentation Process Intensification Framework for Cassava Bio-Refinery in Nigeria

Process intensification in fermentation offers the potential to significantly improve volumetric productivity, reduce capital and operating costs, and enhance product quality in bio-refinery applications. The application of process intensification principles to cassava-based fermentation, a cornerstone of the Nigerian food economy, has not been systematically theorised or empirically validated. This study develops an original theoretical framework for fermentation process intensification in the context of cassava bio-refinery applications, specifically targeting the simultaneous production of lactic acid, ethanol, and single-cell protein from cassava hydrolysate. The theoretical contribution is a kinetic framework that integrates structured metabolic models of Lactobacillus plantarum and Saccharomyces cerevisiae in mixed culture, incorporating substrate competition, product inhibition, and pH-mediated interaction dynamics. The framework is implemented as a set of ordinary differential equations solved using the Runge-Kutta method. Intensification strategies modelled include continuous fermentation with cell recycling, pH-controlled fed-batch operation, and in situ product removal by reactive extraction. Experimental validation is conducted using cassava hydrolysate prepared from TMEB419 cassava from Anambra State (South East) in a 5-litre instrumented bioreactor. Model predictions of biomass concentration, substrate consumption, and product profiles were validated with root mean square errors below 8 percent across fermentation conditions. A techno-economic analysis evaluated the cost reduction achievable through intensified versus conventional batch fermentation. The study represents an original theoretical and experimental contribution to fermentation engineering for tropical starchy feedstocks. Keywords: process intensification, cassava bio-refinery, fermentation kinetics, lactic acid, techno-economic analysis