Biofuel was created from the waste of Greek yogurt
Researchers from the USA and Germany have found a way to use bacteria to process sugars and acids from whey, a byproduct of yogurt production. Biofuels and food additives for feed can be obtained from the waste.
Filtered yogurt, which has gained worldwide fame under the name of Greek, is a traditional product of Eastern Mediterranean cuisine. Filtered through a cloth or paper filter in order to eliminate whey, Greek yogurt has a denser consistency, preserving the characteristic sour taste of yogurt. The increased popularity of the product in recent years is explained by a lower fat content compared to traditional yogurt.
Fermented milk products are produced with a high yield of by-products, such as whey, which contains mainly sugars (lactose and fructose) and lactic acid. Researchers from Cornell University (USA) and the University of Tübingen (Germany), using bacteria, turned sour whey into a mixture of two organic acids – kapron (n-hexane) and caprylic (n-octane). These compounds exhibit antimicrobial properties and can be used as antibiotic food additives for farm animals.
By further processing in the reactors of the resulting mixture of six-, seven-, and eight-atomic acids, chemists synthesized long-chain (up to 14 carbon atoms) molecules of substances from the hydrocarbon class. They are ideal for creating liquid biofuels used for aircraft engines.
Traditionally, biofuels from decomposable waste are obtained under oxygen-free conditions (anaerobic digestion). The researchers used two open reactors with different temperatures: the culture of more thermophilic microbes was heated to 50 °C, the second reactor was maintained at 30 °C.
The living "synthetic chemists" were ordinary intestinal bacteria from the Lactobacillus family. Low temperatures, cheap raw materials, technological simplicity (there is no need to maintain oxygen-free conditions) significantly reduce the cost of the final product compared to previously developed biodegradation technologies, the researchers report. One batch of bacterial cultures can synthesize capronic acid, caprylic acid and secondary products within a few months.
According to the authors, the next stage of the work will be the scaling of the dual bioreactor to factory capacity. So far, the laboratory reactor can produce up to several kilograms of useful compounds per day.
The study was published in the journal Joul (Xu et al., Temperature-Phased Conversion of Acid Whey Waste Into Medium-Chain Carboxylic Acids via Lactic Acid: No External e-Donor).
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