Brassinolide influences the regeneration of adventitious shoots from cultured leaf discs of tobacco

When several concentrations of brassinolide (BL) were added to a shoot induction medium (SIM) that contained only BA, redifferentiation of adventitious shoots from tobacco leaf discs was unaffected at low BL levels (10^-10~10^-8 M), but was inhibited at higher concentrations. In comparison, when BL was applied without BA, only cell expansion occurred and no shoots formed. The determination time for shoot formation was shortened at low BL concentrations, but their formation was postponed (i.e., time was lengthened) at higher concentrations. Elongation of shoots incubated for 30 d was unaffected at low BL concentrations, but was inhibited as that amount increased.NTH1, a tobacco homeobox gene that is expressed in the central zone of the tobacco shoot apex, showed greater expression levels in the SIM over time, and its expression was stronger in media treated with low concentrations of BL compared with the SIM control at the same time point. Expression ofNTH1 was postponed at higher BL concentrations. In conclusion, at low concentrations, brassinolide has no effect on shoot formation. However, it inhibits their formation at high concentrations when cytokinin is included in the media.     

By-product formation in cell-recycled continuous culture of Lactobacillus casei

While the volumetric productivity of lactic acid increased in continuous culture of Lactobacillus casei with cell recycle, enhanced formation of by-products such as acetate, formate, ethanol, and D-lactate was observed in the cell-recycled fermenter compared with a simple chemostat at a similar range of dilution rate. The increased formation of by-product which was significantly dependent on substrate limitation resulted from a lower dilution rate rather than a high cell concentration in the cell-recycled fermenter.     

Rigorous model for spherical cell-support aggregate

The activity of immobilized cell-support particle aggregates is influenced by physical and biochemical elements, mass transfer, and physiology. Accordingly, the mathematical model discussed in this study is capable of predicting the steady state and transient concentration profiles of the cell mass and substrate, plus the effects of the substrate and product inhibition in an immobilized cell-support aggregate. The overall mathematical model is comprised of material balance equations for the cell mass, major carbon source, dissolved oxygen, and non-biomass products in a bulk suspension along with a single particle model. A smaller bead size and higher substrate concentration at the surface of the particle, resulted in a higher supply of the substrate into the aggregate and consequently a higher biocatalyst activity.     

Comparisons of physical properties of bacterial celluloses produced in different culture conditions using saccharified food wastes

The saccharogenic liquid (SFW) obtained by the enzymatic saccharification of food wastes was used as a medium for production of bacterial cellulose (BC). The enzymatic saccharification of food wastes was carried out by the cultivation supernatant ofTrichoderma harziaum FJ1 culture.Acetobacter xylinum KJ1 was employed for the BC production culture. The physical properties, such as polymerization, crystallinity, Young's modulus, and tensile strength, of BCs produced by three culture methods: the static cultures using HS (Hestrin-Schramm) as a reference medium (A) or the SFW medium (B), the shaking culture (C) or the air circulation culture (D) using the SFW medium, were investigated. The degrees of polymerization of BCs produced under the different culture conditions (A∼D) showed 11000, 9500, 8500, and 9200, respectively. Young's modulus was 4.15, 5.0, 4.0, and 4.6 GPa, respectively. Tensile strength was 124, 200, 80, and 184 MPa, respectively. All of the BC had a form of cellulose I representing pure cellulose. In the case of the shaking culture, the degree of crystallinity was 51.2%, the lowest degree. Under the other culturing conditions, the trend should remain in the range of 89.7–84%. Overall, the physical properties of BC produced from SFW were similar to those of BC from HS medium, a commercial complex medium, and BC production by the air circulation culture mode brought more favorable results in terms of the physical properties and its ease of scale-up. Therefore, it is expected that a new BC production method, like air circulation culture using SFW, would contribute greatly to BC-related manufacturing.     

Backbone 1H, 15N, and 13C resonance assignment and secondary structure prediction of HP0495 from Helicobacter pylori

HP0495 (Swiss-Prot ID; Y495_HELPY) is an 86-residue hypothetical protein from Helicobacter pylori strain 26695. The function of HP0495 cannot be identified based on sequence homology, and HP0495 is included in a fairly unique sequence family. Here, we report the sequence-specific backbone resonance assignments of HP0495. About 97% of all the 1HN, 15N, 13Calpha, 13Cbeta, and 13CO resonances were assigned unambiguously. We could predict the secondary structure of HP0495, by analyzing the deviation of the 13Calpha and 13Cbeta shemical shifts from their respective random coil values. Secondary structure prediction shows that HP0495 consists of two alpha-helices and four beta-strands. This study is a prerequisite for determining the solution structure of HP0495 and investigating the protein-protein interaction between HP0495 and other Helicobacter pylori proteins.     

Technological and economic potential of poly(lactic acid) and lactic acid derivatives

Abstract: Lactic acid has been an intermediate-volume specialty chemical (world production ∼ 40,000 tons/yr) used in a wide range of food processing and industrial applications. Lactic acid has the potential of becoming a very large volume, commodity-chemical intermediate produced from renewable carbohydrates for use as feedstocks for biodegradable polymers, oxygenated chemicals, plant growth regulators, environmentally friendly 'green' solvents, and specialty chemical intermediates. The recent announcements of new development-scale plants for producing lactic acid and polymer intermediates by major U.S. companies, such as Cargill, Ecochem (DuPont/ConAgra), and Archer Daniels Midland, attest to this potential.
In the past, efficient and economical technologies for the recovery and purification of lactic acid from crude fermentation broths and the conversion of lactic acid to the chemical or polymer intermediates had been the key technology impediments and main process cost centers. The development and deployment of novel separations technologies, such as electrodialysis (ED) with bipolar membranes, extractive distillations integrated with fermentation, and chemical conversion, can enable low-cost production with continuous processes in large-scale operations. The use of bipolar ED can virtually eliminate the salt or gypsum waste produced in the current lactic acid processes. Thus, the emerging technologies can use environmentally sound processes to produce environmentally useful products from lactic acid. The process economics of some of these processes and products can also be quite attractive. In this paper, the recent technical advances in lactic and polyactic acid processes are discussed. The economic potential and manufacturing cost estimates of several products and process options are presented. The technical accomplishments at Argonne National Laboratory (ANL) and the future directions of this program at ANL are discussed.     

Enhanced Degradation of an Endocrine-Disrupting Chemical, Butyl Benzyl Phthalate, by Fusarium oxysporum f. sp. pisi Cutinase

Compared to yeast esterase, fungal cutinase degraded butyl benzyl phthalate (BBP) far more efficiently; i.e., almost 60% of the BBP disappeared within 7.5 h. Also, the final chemical composition significantly depended on the enzyme used. Toxicity monitoring using bioluminescent bacteria showed that butyl methyl phthalate, a major product of degradation by esterase, was an oxidative toxic hazard.     

Interface resistances of anion exchange membranes in microbial fuel cells with low ionic strength

The interface resistances between an anion exchange membrane (AEM) and the solution electrolyte were measured for low buffer (or ionic strength) of electrolytes typical of microbial fuel cells (MFCs). Three AEMs (AFN, AM-1, and ACS) having different properties were tested in a flat-plate MFC to which 5-mM acetate was fed to the anode and an air-saturated phosphate buffer (PB) solution was fed to the cathode. Current density achieved in the MFCs was correlated inversely with independently measured membrane-only resistances. However, the total interfacial resistances measured by current-voltage plots were approximately two orders higher than those of the membrane-only resistances, although membranes had the same order as with the membrane-only resistance. EIS spectra showed that the resistances from electric-double layer and diffusion boundary layer were the main resistances not the membrane's resistance. The electric-double layer and diffusion boundary layer resistances of the AEMs were much larger in the 10 mM PB electrolyte, compared to 100 mM PB. EIS study also showed that the resistance of diffusion boundary layer decreased due to mechanical stirring. Therefore, the interface resistance that originates from the interaction between the membrane and the catholyte solution should be considered when designing and operating MFC processes with an AEM. The AEMs allowed transport of uncharged O(2) and acetate, but the current losses for both were low during normal MFC operation.     

Cold shock response inLactococcus lactis ssp.diacetylactis

The acquired freeze-thaw tolerance was investigated forLactococcus lactis ssp.diacetylactis. Pretreatment of microorganisms at less severe temperatures to initiate cold tolerance gaveL. lactis ssp.diacetylactis improved cell viability after successive freezings and thawings. The ability of cells to survive freeze-thaw was dependent on factors experienced prior to freezing. Factors affecting lactic acid bacteria survival during freeze-thaw cycles were found to be different diluents, growth phase, and different cold temperatures. Viability experiments showed that this strain displaying cold shock cryotolerance had an improved survival capacity in stationary phase. The plasmid contents of lactic acid bacteria isolated from different types, DRC-2 and DRC-2C, were examined and compared with the plasmid contents of culture collection strains both before and after cold shock treatment. Using agarose gel electrophoresis, no obvious correlation between the cold shock response and the number of plasmids in the cell could be observed.     

Unique Properties of Four Lactobacilli in Amino Acid Production and Symbiotic Mixed Culture for Lactic Acid Biosynthesis

With four Lactobacilli--L. delbrueckii subsp. lactis (ATCC 12315), L. casei (NRRL-B1445), L. delbrueckii (NRRL-B445), and L. heveticus (NRRL-B1937)--the characteristics of cell growth and production of lactate and amino acids were investigated. Especially, the time-course variation in concentration of amino acids (classified into alanine, serine, aspartate, glutamate, aromatic amino acid, and histidine families) was estimated in detail, and the results were systematically compared. It was elucidated that L. delbrueckii (NRRL-B445) and L. helveticus (NRRL-B1937) had quite different characteristics in growth, lactic acid synthesis, and amino acid production. L. helveticus (NRRL-B1937) was superior in the production of amino acids as well as in cell growth, but showed very poor ability in lactic acid production. However, L. delbrueckii (NRRL-B445) showed higher yield of lactic acid despite repressed cell growth, but suffered from severe amino acid deficiency in culture. By modulating the initial concentration of each strain in the mixed culture containing both L. delbrueckii (NRRL-B445) and L. helveticus (NRRL-B1937), the lactic acid production (i.e., the amount of lactic acid produced and lactic acid yield to glucose consumed) was significantly improved, presumably via symbiotic interaction between the two strains.