Conversion of date waste into lactic acid: a sustainable biotransformation approach

Abstract The aim of this study is to identify an environmentally sustainable biotransformation approach to produce lactic acid (LA) from date waste juice using Lactobacillus delbrueckii subsp. bulgaricus (ATCC® 11,842) in batch and fed-batch fermentation. All experiments were performed in duplicate ( n = 2) to ensure reproducibility and data are reported as mean ± standard deviation (SD). The effects of feeding rate (15, 25, and 35 mL/h) of a culture medium containing 60 g/L glucose from date juice were investigated on cell growth, glucose consumption, and LA formation. The fed-batch system with 35 mL/h yielded the highest LA concentration (54.1 ± 1.2 g/L), productivity (0.772 ± 0.018 g/L·h), and yield (1.50 ± 0.03 g/g). Close to complete substrate utilization was noted while residual glucose reduced to 2.0 ± 0.1 g/L. These results show very efficient substrate conversion and reproducible process performance compared with previous studies. The study confirms the technical feasibility of converting locally available date waste into lactic acid through microbial fermentation and provide a scientific basis for future techno-economic and scale-up evaluation toward sustainable bioprocess development.