SBIR-STTR Award

Lactic acid fermentations have been extensively studied in the past decade. Almost all previous studies and current commercial processes use glucose or lactose and very little has been done with starch as the substrate for fermentation. There is a cost advantage in using starch, instead of glucose, for fermentation. The goal of this project is to develop a novel fungal extractive fermentation process to economically produce L(+)-lactic acid from corn meal (starch) generated in a corn dry-milling process. Several new approaches to enhance lactic acid yield and productivity from direct fungal fermentation of starch will be studied in this project. First, immobilization of the mycelial cells in a porous fibrous matrix to control cell morphology and to enhance mass transfer, viable cell density, and reaction rate will be studied. Using immobilized cells with reduced or minimal growth activity should also enhance the lactic acid yield as less carbon source will be used for cell biomass and ATP formation. Second, extractive fermentation to separate lactic acid in situ to reduce product inhibition and to further enhance the fermentation rate will be studied. Lactic acid in the fermentation broth will be separated by solvent extraction in hollow-fiber membrane extractors. It is believed that by selectively removing lactic acid from the fermentation broth continuously, the fermentation pathway can be shifted to produce more lactic acid and less other byproducts.

Anticipated Results/Potential Commercial Applications of Research:
The interest in producing lactic acid from biomass by fermentation is high because of the large potential market for biodegradable poly-lactic acid (PLA) and lactate esters as green solvent. The new fermentation technology developed in this project will provide an energy and cost effective way to make lactic acid and its derivatives from low-cost agricultural commodities and byproducts. A commercial plant to produce lactic acid from corn meals (starch) generated as a byproduct in a corn dry milling plant producing corn protein isolate will be built based on the technology developed in this project.

The ability now exists to take simple starches and convert them into biodegradable plastic products for future generations. Using continuous immobilized fungal fermentation simple starches are converted to a 95% pure stream of L(+)-lactic acid. Commercialization of this biodegradable plastic precursor is being enabled by this project. Increasing the yield, volumetric productivity (g/l/h) and concentration of lactic acid in situ by applying continuous hollow-fiber extractors has proven effective. By simple functions of nature this lactic acid can further be turned into a plethora of other higher valued marketable green products. Thus the commercialization potentials are further improved by having generated several product streams from the one. OBJECTIVES: The interest in producing lactic acid from biomass by fermentation is high because of the large potential market for biodegradable ploy-lactic acid (PLA) and lactate esters as green solvent. The new fermentation technology developed in this project will provide an energy and cost effective way to make lactic acid and its derivatives from low-cost agricultural commodities and byproducts. A commercial bio-refinery is scheduled to be built in Van Wert, Ohio in 2007 for lactic acid production from biomass. APPROACH: Lactic acid fermentations have been extensively studied in the past decade. Almost all previous studies and current commercial processes use glucose or lactose and very little has been done with starch as the substrate for fermentation. There is a cost advantage in using starch, instead of glucose, for fermentation. The goal of this project is to develop a novel fungal extractive fermentation process to economically produce L(+)-lactic acid from corn meal (starch)generated in a corn dry-milling process. Several new approaches to enhance lactic acid yield and productivity from direct fungal fermentation of starch will be studied in this project. First, immobilization of the mycelial cells in a porous fibrous matrix to control cell morphology and to enhance mass transfer, viable cell density, and reaction rate will be studied. Using immobilized cells with reduced or minimal growth activity should also enhance the lactic acid yield as less carbon source will be used for cell biomass and ATP formation. Second, extractive fermentation to separate lactic acid in situ to reduce product inhibition and to further enhance the fermentation rate will be studied. Lactic acid in the fermentation broth will be separated by solvent extraction in hollow-fiber membrane extractors. It is shown that by selectively removing lactic acid from the fermentation broth continuously, the fermentation pathway can be shifted to produce more lactic acid and less other byproducts. Esterfication of lactic acid with alcohols in a novel solvent system with immobilized enzymes also will be evaluated. A prototype process will be constructed and used for cost analysis and preparing sample products for market research and testing