In lactic acid fermentation by Lactobacillus delbrueckii, the produced lactic acid affected the lactic acid productivity. Therefore, for the purpose of alleviating this inhibitory effect, an electrodialysis fermentation method which can continuously remove produced lactic acid from the fermentation broth was applied to this fermentation process. As a result, the continuation of fermentation activity was obtained, and the productivity was three times higher than in non-pH-controlled fermentation. In electrodialysis fermentation, the amount of produced lactic acid was 82.2 g/liter, which was about 5.5 times greater than that produced in non-pH-controlled fermentation. It was concluded that these good results were obtained on account of alleviating the lactic acid inhibitory effect by electrodialysis fermentation. However, the fouling of anion-exchange membranes by cells was observed in electrodialysis fermentation.

Novel Method of Lactic Acid Production by Electrodialysis Fermentation

Lactic acid production from lactose by Lactobacillus plantarum: kinetic model and effects of pH, substrate, and oxygen

Publisher Summary The chapter focuses on the production of lactic acid by microbiological processes. It discusses the chemical and physical properties of the acid followed by its commercial uses. Lactic acid, 2-hydroxypropanoic acid or α-hydroxypropanoic acid, is served as a food preservative in fermented milks, fruits, vegetables, meats, and breads. Various carbohydrate raw materials are used for lactic acid production by bacteria and molds such as refined carbohydrate raw materials; glucose, sucrose, and starch; complex carbohydrates—cellulose, cereal grains, corn, Jerusalem artichokes, and potatoes; and waste materials—cheese whey and permeate, municipal solid waste, and wood molasses. Factors affecting lactic acid concentrations, productivities, and yields include types of process (batch, fed-batch, or continuous), microorganism, strain, inoculum size and nutritional state, temperature, pH, substrate concentration and pretreatment, the presence of competing contaminants in non sterile systems, the presence of bacteriophages, and inhibition by lactic acid with increasing concentrations and by toxic products from substrate pretreatment such as furfural and hydroxymethylfurfural. The chapter also discusses various methods of product recovery and purification namely precipitation and acidification, centrifugation and microfiltration/ultrfiltration, distillation, ion exchange and adsorption, reverse osmosis, and solvent extraction and extractive fermentation. Various types of process controls are also summarized.

Microbiological production of lactic acid.

It is important to produce L(+)-lactic acid at the lowest cost possible for lactic acid to become a candidate monomer material for promising biodegradable polylactic acid. In an effort to develop a high-rate bioreactor that provides high productivity along with a high concentration of lactic acid, the performance of membrane cell-recycle bioreactor (MCRB) was investigated via experimental studies and simulation optimization. Due to greatly increased cell density, high lactic acid productivity, 21.6 g L(-1) h(-1), was obtained in the reactor. The lactic acid concentration, however, could not be increased higher than 83 g/L. When an additional continuous stirred tank reactor (CSTR) was attached next to the MCRB a higher lactic acid concentration of 87 g/L was produced at significant productivity expense. When the two MCRBs were connected in series, 92 g/L lactic acid could be produced with a productivity of 57 g L(-1) h(-1), the highest productivity among the reports of L(+)-lactic acid that obtained lactic acid concentration higher than 85 g/L using glucose substrate. Additionally, the investigation of lactic acid fermentation kinetics resulted in a successful model that represents the characteristics of lactic acid fermentation by Lactobacillus rhamnosus. The model was found to be applicable to most of the existing data with MCRBs and was in good agreement with Levenspiel's product-inhibition model, and the Luedeking-Piret equation for product-formation kinetics appeared to be effective in representing the fermentation kinetics. There was a distinctive difference in the production potential of cells (cell-density-related parameter in Luedeking-Piret equation) as lactic acid concentration increases over 55 g/L, and this finding led to a more precise estimation of bioreactor performance.

High‐rate continuous production of lactic acid by Lactobacillus rhamnosus in a two‐stage membrane cell‐recycle bioreactor

Continuous Production of Lactic Acid from Whey Perméate by Free and Calcium Alginate Entrapped Lactobacillus helveticus

A mathematical model was developed to simulate, on a digital computer, the continuous fermentation of whey lactose to lactic acid with neutralization by ammonia. The simulation predicted the retention times for experimental test and the use of two stages for greatest efficiency. In the experimental tests, Lactobacillus bulgaricus was inoculated into whey in a 14-liter continuous fermentor at 44°C and with automatic pH control. A series of steady-state conditions was managed nonaseptically for 42 days without evident contamination and with an actual increase in the efficiency of conversion. Lactic acid was produced predominately' throughout the period, with less than 0.2% of other compounds. The product contained approximately 8 times as much crude protein (N × 6.25) as the original whey. In a single-stage fermentation at pH 5.5, a retention time of 15 hr resulted in a residual lactose concentration of 0.7%; and little improvement was realized by increasing the retention time. Increasing the pH to 5.8 resulted in a significant improvement, but further increasing the pH to 6.0 resulted in only a small additional gain. By the employment of two fermentors in series at pH 5.5 with a total retention time of 31 hr, the residual lactose was reduced to less than 0.1%. Lactic acid was produced as a function mainly of maintenance rather than growth metabolism.

Continuous lactic acid fermentation of whey to produce a ruminant feed supplement high in crude protein

Systems and methods for processing a high-lactose aqueous fluid (HLAF)(3), such as permeate from ultrafiltration of whey fluid, are described. The preferred process includes concentrating HLAF (3) containing from about 1 to about 35% solids, wherein at least 50% of the solids are lactose, to form a concentrated HLAF (3) containing from about 45 to about 65% solids; further concentrating the HLAF (3) to form a highly concentrated HLAF (3) containing from about 70 to about 80% solids; cooling the highly concentrated HLAF (3) with a gaseous fluid to create a cooling, concentrating, crystallizing cascade to further concentrate the HLAF (3) to form a partially crystallized HLAF (3) containing from about 78 to about 88% solids; and drying the partially crystallized HLAF (3) in an air-lift dryer (24) to form a product rich in crystalling alpha-lactose monohydrate. An air-lift dryer (24) having diverging sidewalls (32) and methods of using same are also disclosed.

Process for drying high-lactose aqueous fluids

An air-lift dryer for processing a high-lactose aqueous fluid (HLAF), such as permeate from ultrafiltration of whey fluid, is provided. The air-lift dryer has an enclosed drying chamber with diverging interior sidewalls that define an intermediate interior space having a cross-sectional area that increases as the diverging interior sidewalls extend away from a lower portion toward an upper portion.

Air-lift dryer for processing high-lactose aqueous fluids

A process comprises concentrating a whey composition to at least about 75 weight % solids in one or more evaporators connected in series to form a concentrated whey composition, wherein at least one of the evaporators comprises an evaporator configured to agitate the whey composition within the at least one evaporator, crystallizing at least a portion of the lactose in the concentrated whey composition in a crystallization cascade comprising one or more crystallizing stages to form an at least partially-crystallized whey composition and drying the at least partially-crystallized whey composition to form a dried whey product.

A. Kent Keller

Papers

Continuous lactic acid fermentation of whey to produce a ruminant feed supplement high in crude protein

Process for drying high-lactose aqueous fluids

Air-lift dryer for processing high-lactose aqueous fluids

Process and system for drying acid whey

System for drying acid whey