The production of L-lactic acid from whey permeate, a waste product of the dairy industry, by fermentation with the lactic acid bacterium L a c t o b a c i l l u s casei subsp, casei was investigated. A fermentation medium consisting of permeate and supplements, which enables exponential growth of the organisms, was developed. A fast method for determination of free and immobilized biomass in solid-rich media, based on measurement of cellular ATP, was evolved. Continuous fermentations in a stirred tank reactor (STR) and in a fluidized bed reactor (FBR) with immobilized biomass were compared. In the STR a volumetric productivity of 5.5 g/1 per hour at 100% substrate conversion [dilution rate (D)---0.22 h -1] was determined. In the FBR porous sintered glass beads were used for immobilization and a maximum biomass concentration of 105 g/ kg support was measured. A productivity of 10 g/l per hour was obtained at D = 0.4 h-1 (substrate conversion 93%) and of 13.5 g/l per hour at D = 1.0 h -1 (substrate conversion 50%).

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The rice pathogen Fusarium fujikuroi is known for producing a wide range of secondary metabolites such as pigments, mycotoxins, and a group of phytohormones, the gibberellic acids (GAs). Bioactive forms of these diterpenes are responsible for hyperelongation of rice stems, yellowish chlorotic leaves, and reduced grain formation during the bakanae disease leading to severely decreased crop yields. GAs are also successfully applied in agriculture and horticulture as plant growth regulators to enhance crop yields, fruit size, and to induce earlier flowering. In this study, six F. fujikuroi wild-type and mutant strains differing in GA yields and the spectrum of produced GAs were cultivated in high-quality lab fermenters for optimal temperature and pH control and compared regarding their growth, GA production, and GA gene expression levels. Comparative analysis of the six strains revealed that strain 6314/ΔDES/ΔPPT1, holding mutations in two GA biosynthetic genes and an additional deletion of the 4'-phosphopantetheinyl transferase gene PPT1, exhibits the highest total GA amount. Expression studies of two GA biosynthesis genes, CPS/KS and DES, showed a constantly high expression level for both genes under production conditions (nitrogen limitation) in all strains. By cultivating these genetically engineered mutant strains, we were able to produce not only mixtures of different bioactive GAs (GA3, GA4, and GA7) but also pure GA4 or GA7. In addition, we show that the GA yields are not only determined by different production rates, but also by different decomposition rates of the end products GA3, GA4, and GA7 explaining the varying GA levels of genetically almost identical mutant strains.

An integrated biological process was developed for the conversion of whey lactose to lactic acid. We report about the achievement of maximum COD reduction and thus a substantial unburdening of the environment, combined with the economic production of lactic acid, appropriate for industrial scale. The process ± designed for continuous operation ± consists of four main steps: (i) Protein recovery by ultra®ltration leading to the ®rst product: protein concentrate. The resulting ®ltrate is the fermentation substrate acid whey permeate. (ii) Adjustment of the composition of the permeate in the medium preparation step in order to ensure the proper function of the following process steps. (iii) Conversion of the lactose to lactate by fermentation with lactic acid bacteria in a cell recycle reactor, using ceramic micro®ltration membranes. (iiii) Conversion of the lactate in the cell-free permeate stream of the fermentation to free lactic acid by bipolar electrodialysis.A stable operation of the process was attained up to more than 2000 hours. Using a new selected strain of lactic acid bacteria, a lactic acid productivity of 17 g l A1 h A1 is achieved at total lactose conversion without any nitrogen supplements like yeast extract. A lactic acid concentration of 190 g l A1 is obtained in the acidic cell of the electrodialysis unit and the COD of the remaining sewage is diminished by 92%. As an additional cost reduction item, the neutralization agent of the fermentation is recovered in the caustic cell of the bipolar electrodialysis unit.A cost evaluation for an industrial scale process (100 000 t of whey per year) resulted in a price of 0.66 $ per kg of lactic acid, which under present terms hits the goal of making this process economic for the large scale production of lactic acid as an attractive building block for various purposes in chemical industry.