Towards Sustainable Lactic Acid Production: Avoiding Gypsum as a Byproduct by using Selective Liquid-Phase Adsorption

Advances in downstream processes and applications of biological carboxylic acids derived from organic wastes

Recovering carboxylic acids derived from organic wastes from fermentation broth is challenging. To provide a reference for future study and industrial application, this review summarized recent advances in recovery technologies of carboxylic acids including precipitation, extraction, adsorption, membrane-based processes, etc. Meanwhile, applications of recovered carboxylic acids are summarized as well to help choose suitable downstream processes according to purity requirement. Integrated processes are required to remove the impurities from the complicated fermentation broth, at the cost of loss and expense. Compared with chemical processes, biological synthesis is better options due to low requirements for the substrates. Generally, the use of toxic agents, consumption of acid/alkaline and membrane fouling hamper the sustainability and scale-up of the downstream processes. Future research on novel solvents and materials will facilitate the sustainable recovery and reduce the cost of the downstream processes.

Tailoring Activated Carbons for Efficient Downstream Processing: Selective Liquid-Phase Adsorption of Lysine

The essential amino acid lysine is of great importance in the nutrition and pharmaceutical industries and is mainly produced in biorefineries by the fermentation of glucose. In biorefineries, downstream processing is often the most energy-consuming step. Adsorption on hydrophobic adsorbents represents an energy, resource, and cost-saving alternative. The results reported herein provide insights into the selective separation of l-lysine from aqueous solution by liquid-phase adsorption using tailored activated carbons. A variety of commercial activated carbons with different textural properties and surface functionalities is investigated. Comprehensive adsorbent characterization establishes structure-adsorption relationships that define the major roles of the specific surface area and oxygen functionalities. A 13-fold increase of the separation of lysine and glucose is achieved through systematic modification of a selected activated carbon by oxidation, and lysine adsorption is enhanced by 30 %.