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The production of nisin, a natural food preservative, by Lactococcus lactis subsp. lactis (ATCC 11454) is associated with the simultaneous formation of lactic acid during fermentation in a whey-based medium. As a result of the low concentration and high separation cost of lactic acid, recovering lactic acid as a product may not be economical, but its removal from the fermentation broth is important because the accumulation of lactic acid inhibits nisin biosynthesis. In this study, lactic acid removal was accomplished by biological means. A mixed culture of L. lactis and Saccharomyces cerevisiae was established in order to stimulate the production of nisin via the in situ consumption of lactic acid by the yeast strain, which is capable of utilizing lactic acid as carbon source. The S. cerevisiae in the mixed culture did not compete with the nisin-producing bacteria because the yeast does not utilize lactose, the major carbohydrate in whey for bacterial growth and nisin production. The results showed that lactic acid produced by the bacteria was almost totally utilized by the yeast and the pH of the mixed culture could be maintained at around 6.0. Nisin production by the mixed culture system reached 150.3 mg/L, which was 0.85 times higher than that by a pure culture of L. lactis .

Biochar was evaluated as a precursor of activated carbon. This product was produced by chemical activation using potassium hydroxide. The effects of operating conditions of activation process, such as temperature, activating agent to biochar mass ratio, and nitrogen flow rate, on the textural and chemical properties of the product were investigated. Activated carbon produced by this method has internal surface area at least 50 times than that of the precursor and is highly microporous, which is also confirmed by scanning electron microscopy analysis. Fourier-transform infrared spectroscopy analysis showed development of aromatization in the structure of activated carbon. X-ray diffraction data indicated the formation of small, two-dimensional graphite-like structure at high temperatures. Thermogravimetric study showed that when potassium hydroxide to biochar mass ratio was more than one, the weight loss decreased.

Management of moisture penetration and hydrolytic degradation of polylactide (PLA) is extremely important during the manufacturing, shipping, storage, and end-use of PLA products. Moisture transport, crystallization, and degradation in PLA have been measured through a variety of experimental techniques including size-exclusion chromatography, differential scanning calorimetry, and X-ray diffraction. Quartz crystal microbalance and dynamic vapor sorption experiments have also been used to measure moisture sorption isotherms in PLA films with varying crystallinity. A surprising result is that, within the accuracy of the experiments, crystalline and amorphous PLA films exhibit identical sorption isotherms.

The conversion of glucose and fructose into gluconic acid (GA) and sorbitol (SOR) was conducted in a batch reactor with free (CTAB-treated or not) or immobilized cells of Zymomonas mobilis . High yields (more than 90%) of gluconic acid and sorbitol were attained at initial substrate concentration of 600 g/L (glucose plus fructose at 1:1 ratio), using cells with glucose-fructose-oxidoreductase activity of 75 U/L. The concentration of the products varied hyperbolically with time according to the equations (GA) = t (GA)_max/(W_GA + t ), (SOR) = t (SOR)_max/(W_SOR + t ), v_GA = [W_GA (GA)_max]/(W_GA + t )^2 and v_SOR = [W_SOR (SOR)_max]/(W_SOR + t )^2. Taking the test carried out with free CTAB-treated cells as an example, the constant parameters were (GA)_max = 541 g/L, (SOR)_max = 552 g/L, W _GA = 4.8 h, W _SOR = 4.9 h, v _GA = 112.7 g/L·h and v _SOR = 112.7 g/L·h.

We developed a metabolically engineered Saccharomyces cerevisiae , which produces optically pure L -lactic acid efficiently using cane juice-based medium. In this recombinant, the coding region of pyruvate decarboxylase (PDC)1 was completely deleted, and six copies of the bovine L -lactate dehydrogenase ( L -LDH) genes were introduced on the genome under the control of the PDC1 promoter. To confirm optically pure lactate production in low-cost medium, cane juice-based medium was used in fermentation with neutralizing conditions. L -lactate production reached 122 g/L, with 61% of sugar being transformed into L -lactate finally. The optical purity of this L -lactate, that affects the physical characteristics of poly- L -lactic acid, was extremely high, 99.9% or over.

A unicellular marine green alga, Chlamydomonas perigranulata , was demonstrated to synthesize starch through photosynthesis, store it in a cell, and ferment it under anaerobic conditions in the dark to produce ethanol, 2,3-butanediol (butanediol), acetic acid, and carbon dioxide (CO_2). Previous fermentation data of an algal biomass cultivated outdoors in a 50-L tubular photo-bioreactor showed good carbon (C) recovery in the fermentation balance, with a higher ratio to alcohols and, therefore, lower ratio to CO_2 in the C distribution of products than what would be expected from the Embden-Myerhof-Parnas pathway. These findings led to a proposed concept for a CO_2-ethanol conversion system (CDECS). The above data were evaluated in terms of hydrogen (H) recovery with the following results: C recovery at 105% was well balanced, although H recovery was as high as 139%, meaning an additional gain of H through fermentation. This finding was reproduced wholly in a set of experiments carried out in the same month of the following year, October, whereas another set of experiments was carried out in the following June provided ordinary fermentation results in terms of C and H recoveries with poor growth. Further analyses of these data revealed that butanediol is equal to ethanol as a product from a putative conversion system from CO_2 to the detected fermentation products, leading to the revision of the CDECS concept to a CO_2-alcohol conversion system (CDACS). The relevance of the CDACS will be discussed in relation to the cultivation conditions employed by chance.

Termites, beetles, and other arthropods can digest living and decaying wood plus other lignocellulosic plant litter. Microbial sources like other wood-eating insect guts and wastewater treatment sludge were screened for lignin depolymerization. Near infrared spectroscopy and atomic force microscopy (AFM) along with high-performance liquid chromatography (HPLC), were used to track changes in functional groups, size, shape, and molecular weight of lignin molecules during incubations. Odontotaenius disjunctus (Betsy beetle) guts dissected whole or separately as midgut, foregut, and hindgut, consumed corn stover but did not show lignin depolymerization. The sludge-treated lignin did show some reduction in molecular weight on the HPLC, particle size (350–650 nm initially to 135–220 nm by day 30) and particles per field on AFM. pH and the presence of nutrients had a substantial effect on the extent of depolymerization. Cultures in lignin and nutrients showed higher growth than cultures with lignin only. Colony characteristics within the beetle gut and the sludge were also evaluated.

Lactic acid is used as a food additive for flavor and preservation and a precursor in the development of poly-lactic acid, a product used to make biodegradable plastics and textiles. Rhizopus oryzae NRRL 395 is known to be a strain that produces optically pure L -(+)-lactic acid. The morphology of Rhizopus cultures is complex, forming filamentous, clumps, and pellet mycelia. Different morphology growth has significant effects on lactic acid production. In bioreactors, the filamentous or clump mycelia increase the viscosity of the medium, wrap around impellers, and block the nutrient transportation, leading to a decrease in production efficiency and bioreactor performance. Growing fungi in pellet form can significantly improve these problems. In this study, factors that affect lactic acid production in pelletized flask cultures using R. oryzae NRRL 395 were investigated in detail. Completely randomized designs were used to determine the influence of culture temperature, time, concentration of glucose, and inoculum size. Lactic acid fermentation using clump and pellet morphologies were performed in a 5 L fermentor at the optimal values obtained from flask culture. Finally, fed-batch culture was used to enhance the lactate concentration in broth. The final lactate concentration of fed-batch culture reached 92 g/L. The data presented in the article can provide useful information on optimizing lactic acid production using alternative source materials.

Gram-positive bacteria have been explored to convert lignocellulosic biomass to biofuel and bioproducts. Our long-term goal is to create genetically engineered lactic acid bacteria (LAB) strains that convert agricultural biomass into ethanol and other value-added products. The immediate approaches toward this goal involve genetic manipulations by either introducing ethanol production pathway genes or inactivating pathways genes that lead to production of undesired byproducts. The widely studied species Lactobacillus plantarum is now considered a model for genetic manipulations of LAB. In this study, L. plantarum TF103 strain, in which two of the chromosomal L- ldh and D- ldh genes are inactivated, was used to introduce additional mutations on the chromosome to eliminate undesired fermentation products. We targeted the acetolactate synthase gene ( als ) that converts pyruvate to acetolactate, to eliminate the production of acetoin and 2,3-butanodial. A pBluescript derivative containing sections of the als coding region and an erythromycin resistance gene was directly introduced into L. plantarum TF103 cells to create mutations under selection pressure. The resulting erythromycin resistant (Em^r) TF103 strain appears to have chromosomal mutations of both the als and the adjacent lysP genes as revealed by polymerase chain reaction and Southern blot analyses. Mutations were thus generated via targeted homologous recombination using a Gram-negative cloning vector, eliminating the use of a shuttle vector. This method should facilitate research in targeted inactivation of other genes in LAB.

Agrobacterium isolated from soil samples produced two extracellular polysaccharides: succinoglycan, an acidic soluble polymer, and curdlan gum, a neutral, insoluble polymer. Maize glucose, cassava glucose, and maize maltose were used in fermentation medium to produce insoluble polysaccharide. Two Agrobacterium sp. strains which were used (ATCC 31749 and IFO 13140) in the production of insoluble exopolysaccharide presented equal or superior yields compared to the literature. The strain ATCC 31749 yielded better production when using maize maltose, whose yield was 85%, whereas strain IFO 13140 produced more when fed maize glucose, producing a yield of 50% (on reducing sugars).