Lactic acid is a relatively cheap chemical with a wide range of applications:
as a preservative and acidifying agent in food and dairy industry, a monomer
for biodegradable poly-lactide polymers (PLA) in pharmaceutical industry,
precursor and chemical feedstock for chemical, textile and leather
industries. Traditional raw materials for fermentative production of lactic
acid, refined sugars, are now being replaced with starch from corn, rice and
other crops for industrial production, with a tendency for utilization of
agro industrial wastes. Processes based on renewable waste sources have
ecological (zero CO2 emission, eco-friendly by-products) and economical
(cheap raw materials, reduction of storage costs) advantages. An intensive
research interest has been recently devoted to develop and improve the lactic
acid production on more complex industrial by-products, like thin stillage
from bioethanol production, corncobs, paper waste, straw etc. Complex and
variable chemical composition and purity of these raw materials and high
nutritional requirements of Lare the main obstacles in these production
processes. Media supplementation to improve the fermentation is an important
factor, especially from an economic point of view. Today, a particular
challenge is to increase the productivity of lactic acid production on
complex renewable biomass. Several strategies are currently being explored
for this purpose such as process integration, use of Lwith amylolytic
activity, employment of mixed cultures of Land/or utilization of
genetically engineered microorganisms. Modern techniques of genetic
engineering enable construction of microorganisms with desired
characteristics and implementation of single step processes without or with
minimal pre-treatment. In addition, new bioreactor constructions (such as
membrane bioreactors), utilization of immobilized systems are also being
explored. Electrodialysis, bipolar membrane separation process, enhanced
filtration techniques etc. can provide some progress in purification
technologies, although it is still remaining the most expensive phase in the
lactic acid production. A new approach of parallel production of lactic
bacteria biomass with probiotic activity and lactic acid could provide
additional benefit and profit rise in the production process.
Time-delay mathematical model of lagged lactic acid production using agro-industrial wastes as substrate
