Preliminary parameter determination for optimised lactic acid production using Lacticaseibacillus casei: Defining critical variables for Taguchi-based process optimization.

Abstract

The Taguchi method is widely recognized for its efficacy in multifactorial experimental optimization; however, the precision of its outcome is critically dependent on thorough preliminary parameter determination and effective screening of process variables. In this study, key parameters influencing lactic acid fermentation were systematically identified and evaluated using Lacticaseibacillus casei FWL020—selected for its robust antimicrobial activity and notable metabolic potential. Preliminary evaluations using the One Variable at a Time (OVAT) approach examined the effects of dextrose (1%–8%) and various nitrogen sources—yeast extract, bacteriological peptone, and papaic digest of soya peptone—on bacterial growth and metabolite yield. Among the tested conditions, papaic digest of soya peptone (1.5%) combined with 5% dextrose produced the highest lactic acid concentration (9.3 mg/g), as confirmed by FeCl₃-based colorimetric assays. These findings provided a robust foundation for parameter selection, enabling the strategic implementation of Design of Experiments (DOE). The outcomes underscore the necessity of empirical variable determination prior to statistical modeling, thereby enhancing the efficacy and reproducibility of Taguchi-based optimization for scalable lactic acid production.