Resonance Raman spectra of chlorophylls dissolved in liquid crystal matrices. III. Orientational distribution function of chlorophyll b in an MBBA + EBBA liquid crystalline matrix

Polarized resonance Raman spectra of chlorophyll (Chl) b oriented in a mixture of p-methoxybenzylideno-p'-butylaniline (MBBA) and p-ethoxybenzylideno-p'-butylaniline (EBBA) have been measured. The spectra have been analyzed and the second- and fourth-rank order parameters and the orientational distribution function of Chl b are presented.     

Purification and Characterization of an Aminopeptidase from Lactococcus lactis subsp. cremoris AM2

An aminopeptidase was purified from cell extracts of Lactococcus lactis subsp. cremoris AM2 by ion-exchange chromatography. After electrophoresis of the purified enzyme in the presence or absence of sodium dodecyl sulfate, one protein band was detected. The enzyme was a 300-kilodalton hexamer composed of identical subunits not linked by disulfide bridges. Activity was optimal at 40 degrees C and pH 7 and was inhibited by classical thiol group inhibitors. The aminopeptidase hydrolyzed naphthylamide-substituted amino acids, as well as dipeptides and tripeptides. Longer protein chains such as the B chain of insulin were hydrolyzed, but at a much slower rate. The Michaelis constant (K(m)) and the maximal rate of hydrolysis (V(max)) were, respectively, 4.5 mM and 3,600 pkat/mg for the substrate l-histidyl-beta-naphthylamide. Amino acid analysis showed that the enzyme contained low levels of hydrophobic residues. The partial N-terminal sequence of the first 19 residues of the mature enzyme was determined. Polyclonal antibodies were obtained from the purified enzyme, and after immunoblotting, there was no cross-reaction between these antibodies and other proteins in the crude extract.     

Infectious disease and the Unesco basic education initiative

As part of a Basic Education for All campaign, Unesco is exploring ways to improve health and nutrition in school-age children in order to help them take advantage of the only schooling they may ever receive. At the first international Unesco working meeting on health, nutrition and school performance, intestinal helminths were identified as more appropriate immediate targets than malaria and other infectious diseases. Prevalence and intensity of infection in school-age children, the schools as vehicles of intervention, and the availability of interventions contributed to this choice. However, there are still many gaps in our knowledge of the effects of infectious diseases in schoolchildren. Through the improvement of understanding in this area, the parasitology community may be able to contribute to the Unesco project.     

BCG: a modifier of immune responses to parasites

The use of BCG (Bacille Calmette-Guerin) as an adjuvant is well-established for vaccination against leprosy and tuberculosis. Dominique Frommel and Phillippe Lagrange discuss the effects of BCG in the control of parasite infections, particularly leishmaniasis, and the possibility of the development of anti-parasite recombinant BCG vaccines.     

RAMARIA SUBGENERA RAMARIA AND LAETICOLORA IN YUNNAN

Three taxa of Ramaria subgenus Ramaria, and 18 of subg. Laeticolora are reported from Yunnan Province. Of these 13 are considered new to science. Only one taxon (R. formosa) is considered of widespread distribution, the others being known olay from the Indo-Asian subcontinent. Wide distribution patterns, based on phenetic similarity, seem to be at the infraspecific to species complex level, but only rarely contaxie. New taxa are as follows: subg. Ramaria: R. eryuanensis; subg. Laeticolora: R. brunneipes, R. distinctissima, R. ephemeroderma, R. hilaris, R. lacviformosoides, R. linearioides, R. linearis, R. nanispora, R. rubri-attenuipcs, R. sino-conjunctipes, R. rubricarnata var. laeta, R. botrytoides var. microspora, and R. neoformosa var. sinensis. Keys to Yunnan taxa of Ramaria subgenera Ramarla and Laeticolora are furnished.     

Recycle use of immobilized glucoamylase by tangential flow filtration unit

Various properties of glucoamylase immobilized onto corn stover supporting material and separation of immobilized enzyme by tangential flow filtration unit were studied. Optimum pH and temperature of immobilized enzyme were 3.5 and 60 degrees C, respectively. Enzyme stability was studied in a packed-bed column. The starch conversion rate was attained at 81% for 15 days; after that, the hydrolysis rate gradually decreased. Size of supporting material proved to be an important factor, with higher activity and good loading yield resulting from smaller supporting material. Glucoamylase immobilized onto supporting material less than 44 mum was used for hydrolysis of 10% soluble starch at pH 3.5 and 40 degrees C for 3 h. Then immobilized glucoamylase was separated from the product by means of a tangential flow filtration unit using a 0.2-mum pore size Nylon 66 membrane filter. This operation was continued until 180 ml filtrate was obtained from a 260-mL starting volume. Then, the next batch was started by adding 180 mL starch substrate into the reactor. The batchwise experiments were repeated 20 times. The average filtration rate of each batch was determined and found to sharply decline during the first four batches. Thereafter, it gradually decreased from batch to batch. The cause of decreasing filtration rate appeared to be due to retrogradation of starch. The percentage of starch hydrolysis within 20 batches was in the range 89-96%. The filtration rate becomes higher if the hydrolyzation time is extended to 14 h. Resistance to filtration was also investigated. Almost all of the total resistance is related to insoluble materials, with the significant part of this from the resistance due to insoluble materials deposited on a surface of membrane and boundary layer resistance. Using a microscopic method, no microorganisms were found in the filtrate.     

Effect of environmental growth conditions on plasmid stability, plasmid copy number, and catechol 2,3-dioxygenase activity in free and immobilized Escherichia coli cells

In order to better understand the high plasmid stability in immobilized recombinant E. coli cells, the effects of dilution rate on the pTG201 plasmid stability, the copy number, and the catechol 2,3-dioxygenase (encoded by XyIE gene) production were, at first, studied in free E. coli W3101 continuous cultures in minimal media. It was found that decreasing specific growth rate increased the plasmid copy number and the catechol 2,3-dioxygenase activity but the stability decreased. In continuous culture with immobilized cells, an increase was shown in plasmid copy number and catechol 2,3-dioxygenase activity probably due to the distribution of growth in the gel beads. Besides mechanical properties of gel beads which may allow limited cell divisions, the increase in plasmid copy number is involved in enhanced plasmid stability in immobilized cells. In the same way, an experiment conducted in LB medium dealing with competition between pTG201-free and pTG201-containing E. coli B cells was described. It was shown that the competition was not more pronounced in gel bead compared to a free system. The effects of nutritional limitations on pTG201 plasmid stability and catechol 2,3-dioxygenase activity during chemostat cultivations in free and immobilized E. coli B cells were also investigated. It was found that immobilization of cells increased the stability of pTG201 even under glucose, nitrogen, or phosphate limited cultures. However in the case of magnesium depleted culture, pTG201 was shown to be relatively instable and a decrease in viable cell number during the immobilized continuous culture was observed. By contrast to the free system, the catechol 2,3-dioxygenase activity increased in immobilized cells under all culture conditions used.     

Sliding controller design for a nonlinear fermentation system

The design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.     

Reactive extraction of penicillin G from mycel-containing broth in a countercurrent extraction decanter

Penicillin was recovered from mycel-containing fermentation broth by direct reactive extraction into a counter-current extraction decanter, Type CA 226-290 of the Westfalia Separator Co., at room temperature via steady state operation. Penicillin concentrations in the feed varied from 3 to 41 g L(-1), Amberlite LA-2 carrier concentrations from 7 to 20 g L(-1)and/or DITDA carrier concentrations from 7.2 to 84 g L(-1), the LA-2-to-penicillin mole concentration ratio from 4 to 6.4, and/or the DITDA-to-penicillin mole concentration ratio was maintained at 2. The throughputs of the fermentation broth (520 to 880 L h(-1)) of the solvent phase (200 to 860 L h(-1)) and the over all throughput (800 to 1750 L h(-1)) were high. Extraction degrees of 72 to 96% were achieved between pH 4.6 and 5.1. Without carriers in the same pH range, extraction degrees of only 17 to 19% were attained. By reducing the pH to 2.3 and in the absence of carriers, the degree of extraction was increased to 61%. However, during the extraction, 6.5% of the penicillin decomposed. At these high throughputs, the steady state was attained within 1 to 4 min. Through the mechanical stress, the length of the hyphae was reduced and the protein content of the broth was increased by 50 to 100%. However, this protein content had no appreciable influence on the phase separation.