Optimization of lactic acid production from sugar cane

Abstract

Lactic acid is a compound widely used in food, pharmaceutical, medical and chemical industries. Produced from sugars, through biochemical route by fermentation, it has emerged as a potential chemical compound, for the synthesis of renewable and biodegradable plastics, as well as possible precursor for other molecules. The monomer for the Polylactic Acid (PLA) production is highlighted by its versatility to use and its promising characteristics, such as biodegradability, biocompatibility, elasticity, and a good profile for controlled release of drugs. However, its use on industrial scale is still limited due to the relatively high cost of its production, when compared to petrochemical via, It occurs naturally as two optical isomers, D(-) and L(+) lactic acid. Regarding biomaterial applications, the lactic acid enantiomeric purity is also a crucial parameter to the manufacture of biodegradable polymers and plastics, since this affects the physical properties of the PLA. The crystallinity and many other important physical properties such as degradation rates are controlled by the ratio of the enantiomers D(-) and L(+) used. Due to the need of lactic acid enantiomeric purity of in the chemical industry, the production of lactic acid via fermentation has been more efficient when compared to chemical via production. However, in order to the lactic acid produced by fermentation be economically competitive compared to the petrochemical based plastics, it is necessary to keep low costs that is linked to process performance and raw material prices. Therefore, carbon sources such as pentose or hexose from lignocellulose residues can be quite promising, due to mainly, preventing the competition with food supply as well as relatively cheapness, besides being abundant and renewable. Moreover, reusing waste sources has been of increase interest due to environmental concerns and legislation. This has motivated the industry to consider lignocellulose residues as a carbon source for production. Bearing all this in mind, it is clear that the production of lactic acid by fermentation has several advantages when compared to chemical synthesis, such as high yield, low cost of substrates, relatively low temperatures, and low energy consumption. In this sense the objective of this research work is to optimize the lactic production by fermentation of sugars and to propose and evaluate the molecular distillation based process to purify the lactic acid from broth. As carbon sources will be considered sugar cane molasses and hexoses and pentose obtained from sugar cane bagasse hydrolyses. (AU)