How to Turn Apple Pomace and Whey Waste into Succinic Acid?

Food industries generate huge amounts of waste: apple pomace left after juicing and whey from milk processing. Researchers found that the bacterium Basfia succiniciproducens can turn these leftovers into valuable organic acids, especially succinic acid, a building block for bioplastics and solvents. After thermal pretreatment, the apple pomace served as “food” for the microbes, yielding 0.224 g of succinic acid per gram of consumed sugar, plus small amounts of lactic, formic and acetic acids. With whey, the results were even better: 0.236 g of succinic acid per gram of lactose, plus formic and acetic acids. These figures show lactose is a very promising carbon source for organic‑acid production. This is the first study to propose apple pomace as a substrate for this bacterium, paving the way for greener, waste‑reducing chemical processes. In the future, such biotech could make the production of chemical feedstocks cheaper and more sustainable.

Basfia succiniciproducens is a Gram‑negative bacterium belonging to the Rhodospirillaceae family, known for fermenting both five‑ and six‑carbon sugars. Its key metabolic route is the succinic fermentation pathway, where pyruvate is converted to succinic acid via succinate phosphate. During this process, energy is conserved as ATP through substrate‑level phosphorylation, making the pathway more efficient than traditional lactic fermentation. Thermal pretreatment of apple pomace breaks down fiber cell walls, releasing sugars such as glucose, fructose, and pectin, which are rapidly taken up by the bacterium. In whey, lactose is hydrolyzed into glucose and galactose by a β‑galactosidase expressed by the strain, providing a more homogeneous carbon source. Formic and acetic acid production stems from a mixed‑acid fermentation, where pyruvate is decarboxylated to acetyl‑CoA, then converted to acetate or reduced to formate. The yield of 0.236 g/g succinic acid on lactose indicates an optimized redox balance, with a favorable NADH/NAD⁺ ratio for pyruvate reduction. Moreover, B. succiniciproducens tolerates high concentrations of organic acids, making the process scalable in industrial bioreactors where pH can be controlled to maximize production. Future optimizations could involve metabolic engineering to increase expression of key enzymes such as succinate dehydrogenase and reduce by‑product formation, further improving yield and purity of the produced succinic acid.