Lactic acid production from alternative nitrogen sources

Abstract

Lactic acid is a versatile chemical whose demand is increasing driven primarily by the production of biodegradable lactic acid polymers, and to a lesser extent, solvents lactate, and various other compounds obtained from three-carbon molecules, precursors of high commercial importance. The microbial production of lactic acid requires the availability of sources of carbon, nitrogen, phosphorus and micronutrients. Although the carbon source is the one used on a larger scale, we must pay attention also to the sources of the others nutrients. As lactic acid bacteria has a considerable demand for organic nitrogen since the nutritional requirements are met not only by inorganic salts and also require more complex nutrients such as amino acids and peptides for growth. Thus the culture medium normally contains nitrogen complex supplements, particularly protein hydrolysates, considered along with the carbon source, supplements with the highest costs in fermentation media. The main objective of this work is to study the microbial production of lactic acid using alternative nitrogen sources. The main sources of nitrogen that can be applied due to the abundance and ease of production technologies (well-defined) are: corn steep liquor, whey protein, soy protein (fresh, or hydrolyzed peptone), vinasse (ethanol plant) and flours of animal waste. Thus, the substitution for lower cost nutrient may indicate a decrease of the costs involved in production, a necessary step aiming the large scale production of "commodity" type molecules.(AU)