Biostrategic removal of cadmium from agricultural products: Mixed lactobacillus-mediated fermentation-elution cascade

• Mixed-LAB fermentation significantly reduced Cd levels of Cd-polluted crops. • Post-fermentation starch purity reached 95.2% (rice) and 94.7% (mung bean). • This fermentation might cause protein and mineral loss in agricultural products. • “Release-fixation-separation” synergy was established for efficient Cd removal. Heavy metal pollution has resulted in severe environmental issues. The growth and development of crops in cadmium (Cd)-contaminated soil are inhibited, and the edible parts often exceed Cd safety standards, posing significant risks to human health. Therefore, it is crucial to minimize the Cd concentration in cereals. Microbial fermentation has been shown to be an effective strategy for removing Cd from these contaminated cereals. In this study, raw rice grains with a Cd concentration of 1.80 mg kg⁻¹ and mung beans with a Cd concentration of 0.90 mg kg⁻¹ were used as experimental materials. We employed single-factor and response surface optimization experiments to investigate three mixed lactobacillus (mixed-LAB) fermentation on rheological and sensory properties of rice flour. It was established that Cd is uniformly distributed in the endosperm of the contaminated rice grains based on X-ray fluorescence scanning. The mixed-LAB fermentation process was implemented for rice flour with exceeding Cd. After fermentation, the products were centrifuged at 6000 rpm to separate the components. The sediment was washed with five volumes of deionized water. The optimized conditions were determined as follows: 9% volume of mixed-LAB fermentation, 29 h of the fermentation time, 5:1 of the liquid-material ratio, and 34°C of the fermentation temperature. This fermentation process significantly enhanced the quality of fermented rice flours and starch purity. This fermentation method applied to Cd-contaminated mung bean flour with a Cd level of 0.90 mg kg⁻¹ significantly decreased the Cd level to 0.11 mg kg⁻¹, achieving an 88% Cd removal rate. Following fermentation, the starch purity of the mung bean flour reached approximately 94%, and the mung bean starch exhibited enhanced coagulation ability and superior toughness. Our findings demonstrate that mixed-LAB fermentation is an effective technique for removing Cd from agricultural products contaminated with Cd levels exceeding safety standards. However, it increased starch purity while causing protein loss. Furthermore, fermentation-derived Cd-containing wastewater treatment has not yet been addressed.