Submitted to: Biotechnology Letters
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2000
Publication Date: N/A
Citation: Interpretive Summary: Alfalfa is a perennial legume, which means that it fixes its own nitrogen fertilizer from the atmosphere and only needs to be reseeded every 3-5 years. It produces more protein per acre than any other crop and is known for its good soil and water conservation characteristics. These characteristics make it a highly sustainable and desirable crop that improves yields of other crops grown in rotation with it. Utilization of alfalfa, however, has been limited to ruminant (cattle, sheep, and goats) rations by the high fiber content of the herbage. This limitation can be overcome by a process called wet fractionation, the separation of freshly cut herbage into juice and fiber fractions, each of which can be converted to valuable products. The fiber fraction was converted to sugars by properly selected enzymes. These sugars, in turn, were fermented to industrial chemicals or fuels such as lactic acid or ethanol. It is important to determine the proper mix and quantity of enzymes to convert fibers to sugars and to determine the most appropriate microorganisms to ferment these sugars to the target products(s). Knowledge of the quantity and value of products relative to input costs is necessary to determine economic feasibility. More than 40g of lactic acid was produced per 100g alfalfa fiber processed. The production of chemical feedstocks from renewable biological materials can help to reduce the release of carbon dioxide to the atmosphere, reduce dependence on imported petroleum, as well as providing new jobs in the rural sector.
Technical Abstract: Various agriculture feedstock residues were evaluated for lactic acid production by simultaneous saccharification and fermentation (SSF) using Lactobacillus delbrueckii and Lactobacillus plantarum, without any additional nutrients. Lactic acid production was higher in alfalfa fiber and soya fiber compared to corn cob (soft) and wheat straw. In Lactobacillus plantarum, the amount of lactic acid obtained from alfalfa fiber and soya fiber was 46 and 44/100 g fiber respectively. However, in Lactobacillus delbrueckii, the lactic acid production in soya fiber was 44 g/100 g fiber and that of alfalfa was 32 g/100 g fiber. Small amounts of acetic acid were also produced from SSF of agricultural feedstocks residues. During SSF of alfalfa fiber, lactic acid production in both L. delbrueckii and L. plantarum was enhanced by addition of increased concentrations of mixtures of pectinases and cellulases. Also the lactic acid production from alfalfa fiber did not change with increasing O2 transfer rates in the fermentation medium, whereas acetic acid production in both Lactobacillus cultures increased with increasing O2 transfer rates.