Biomedical subjects

M Mota

Publications and source records attributed to M Mota.

At least 37 records · Page 2Linked to original sources

PubMed2002

Studies on the properties of Celluclast/Eudragit L-100 conjugate.

A cellulase from Trichoderma reesei was immobilized on Eudragit L-100, a reversibly soluble polymer depending on the pH of the medium. The solubility of the modified cellulase was studied at different pH values. By changing the pH, the adsorption equilibrium of the derivatized proteins is switched towards the liquid phase, thus making recycling possible. This method allows for improved stability, without major loss of specific activity. The adsorption of cellulase on Eudragit lowers the enthalpy of denaturation, but affects only slightly the denaturation temperature. The use of carbodiimide was ineffective on linking the enzymes covalently to the polymer, since the immobilization process was found to be only mediated by non-covalent forces.

Adsorption↗

PubMed2002

Oxidative stress response of Kluyveromyces marxianus to hydrogen peroxide, paraquat and pressure.

The aim of this work was to study the oxidative stress response of Kluyveromyces marxianus to hydrogen peroxide (50 mM), paraquat (1 mM), an increase in air pressure (120 kPa, 600 kPa) and pure oxygen pressure (120-600 kPa) in a pressurized bioreactor. The effect of these oxidants on metabolism and on the induction of antioxidant enzymes was investigated. The exposure for 1 h of K. marxianus at exponential growth phase with either H(2)O(2) or paraquat, under air pressure of 120 kPa or 600 kPa, induced an increase in both superoxide dismutase (SOD) and glutathione reductase (GR) content. SOD induction by the chemical oxidants was independent of the air pressure values used. A 2-fold increase in SOD activity was observed after 1 h of exposure to H(2)O(2) and a 3-fold increase was obtained by the presence of paraquat, with both air pressures studied. In contrast, GR activity was raised 1.7-fold by the exposure to both chemicals with 120 kPa, but a 2.4-fold GR induction was obtained with 600 kPa. As opposed to Saccharomyces cerevisiae, catalase was not induced and was even lower than the normal basal levels. This antioxidant enzyme seemed to be inhibited under increasing oxygen partial pressure. The cells showed a significant increase in SOD and GR activity levels, 4.7-fold and 4.4-fold, when exposed for 24 h to 120 kPa pure oxygen pressure. This behaviour was even more patent with 400 kPa. However, whenever cells were previously exposed to low air pressures, low enzymatic activity levels were measured after subsequent exposure to pure oxygen pressure.

Antioxidants↗

PubMed2002

Anaerobic degradation of oleic acid by suspended and granular sludge: identification of palmitic acid as a key intermediate.

The aim of the present work was to study the maximum potential methane production in batch assays of sludge samples taken along the operation of two EGSB reactors (RI inoculated with granular sludge and RII inoculated with suspended sludge) fed with increasing oleic acid concentrations between 2 and 8 gCOD/l (HRT = 1 day). After removing the residual substrate, the sludge was incubated in batch vials without any added carbon source. A maximum methane production rate of 152+/-21 mlCH4(STP)/gVS.day was obtained for the suspended sludge taken on day 70, when oleate at a concentration of 2 g COD/l was fed with a co-substrate (50% COD). The maximum plateau achieved in the methane production curve was 1145+/-307 mlCH4(STP)/gVS, obtained for the suspended sludge taken on day 162, when oleate was fed as the sole carbon source at 6 g COD/I. The methanization rate of the adsorbed substrate was enhanced under stirring conditions and was inhibited by adding oleic acid. Extraction and GC analysis confirmed that the main adsorbed substrate was palmitate, and not oleate. Accumulated palmitate adsorbed onto the sludge and further beta-oxidation was inhibited when in the presence of oleic acid. If oleic acid was removed from the medium beta-oxidation proceeded with methane production. Suspended sludge was more efficient than granular sludge.

Adsorption↗

PubMed2001

Evidence for a role of mixed lineage kinases in neuronal apoptosis.

Superior cervical ganglion (SCG) sympathetic neurons die by apoptosis when deprived of nerve growth factor (NGF). It has been shown previously that the induction of apoptosis in these neurons at NGF withdrawal requires both the activity of the small GTP-binding protein Cdc42 and the activation of the c-Jun N-terminal kinase (JNK) pathway. The mixed lineage kinase 3 (MLK3) belongs to a family of mitogen-activated protein (MAP) kinase kinase kinases. MLK3 contains a Cdc42/Rac interactive-binding (CRIB) domain and activates both the JNK and the p38 MAP kinase pathways. In this study the role of MLK3 in the induction of apoptosis in sympathetic neurons has been investigated. Overexpression of an active MLK3 induces activation of the JNK pathway and apoptosis in SCG neurons. In addition, overexpression of kinase dead mutants of MLK3 blocks apoptosis as well as c-Jun phosphorylation induced by NGF deprivation. More importantly, MLK3 activity seems to increase by 5 hr after NGF withdrawal in both differentiated PC12 cells and SCG neurons. We also show that MLK3 lies downstream of Cdc42 in the neuronal death pathway. Regulation of MLK3 in neurons seems to be dependent on MLK3 activity and possibly on an additional cellular component, but not on its binding to Cdc42. These results suggest that MLK3, or a closely related kinase, is a physiological element of NGF withdrawal-induced activation of the Cdc42-c-Jun pathway and neuronal death. MLK3 therefore could be an interesting therapeutic target in a number of neurodegenerative diseases involving neuronal apoptosis.

Amino Acid Motifs↗

PubMed2001

Effect of airflow rate on yields of Steinernema carpocapse Az 20 in liquid culture in an external-loop airlift bioreactor.

Maximization of the contact between males and females is a key factor in the production of the nematode Steinernema carpocapsae in a bioreactor.%The influence of the airflow rate in male and female distribution and mass production in an external-loop bioreactor with a deceleration zone was studied. When operating at an airflow rate of 0.05 vvm, a high retention of females in the deceleration zone of the bioreactor was observed and a larger nematode productivity was obtained. At this aeration rate there was a higher proportion of males in that zone, which together with the lower circulation rate, increases the probability of encounters, thereby explaining the increase in productivity.

Air Movements↗

PubMed2001

Effect of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part I: Biofilm growth and activity.

Two similar anaerobic fixed-bed bioreactors which allowed the biomass to be periodically withdrawn were run in parallel. After feeding each digester with synthetic dairy wastes of different lipid content (Period I), both digesters were fed with increasing sodium oleate concentrations with skim milk as co-substrate (Period II) and oleate as the sole carbon source (Period III). In Period I, the digester fed with lipids was more efficient and exhibited lower levels of volatile fatty acids than the digester fed without lipids. The biofilm built up in the presence of lipids was thinner, but more resistant to the presence of oleate than the biofilm formed in the absence of lipids, which lost 53% of its solids after contacting with oleic acid. The specific methanogenic activity with butyrate as substrate was enhanced in the presence of lipids, but no significant effect was detected on the acetoclastic and hydrogenophilic activities, which remained similar for both digesters along the trial period.

Anaerobiosis↗

PubMed2001

Effects of lipids and oleic acid on biomass development in anaerobic fixed-bed reactors. Part II: Oleic acid toxicity and biodegradability.

Oleic acid toxicity and biodegradability were followed during long-term operation of two similar anaerobic fixed-bed units. When treating an oleate based effluent, the sludge from the bioreactor that was acclimated with lipids during the first operation period, showed a higher tolerance to oleic acid toxicity (IC50 = 137 mg/l) compared with the sludge fed with a non-fat substrate (IC50 = 80 mg/l). This sludge showed also the highest biodegradation capacity of oleic acid, achieving maximum methane production rates between 33 and 46 mlCH4(STP)/gVS.day and maximum percentages of methanization between 85 and 98% for the range of concentrations between 500 and 900 mg oleate/l. When oleate was the sole carbon source fed to both digesters, the biomass became encapsulated with organic matter, possibly oleate or an intermediate of its degradation, e.g. stearate that was degraded at a maximum rate of 99 mlCH4(STP)/gVS.day. This suggests the possibility of using adsorption-degradation cycles for the treatment of LCFA based effluents. Both tolerance to toxicity and biodegradability of oleic acid were improved by acclimatization with lipids or oleate below a threshold concentration.

Biodegradation, Environmental↗

PubMed2001

Trends in the use of protozoa in the assessment of wastewater treatment.

Increasing environmental pollution and the continuous development of new chemicals and drugs has led to ever growing concern about the potential effects of these compounds directly or indirectly on human health. As concerns water pollution, protozoa seem to be an excellent tool to assess both toxicity and pollution: they are regarded as biological indicators of pollution when their presence or absence can be related to particular environmental conditions, and they are considered test organisms when a species or population is used to evaluate the toxicity of relevant toxic compounds. Thus, an integrated approach is being developed to assess how toxic compounds affect the different biological levels of organisation--from the community level to the species level--of ciliated protozoa. The present paper reports and discusses the current state of the art of this approach.

Animals↗

PubMed2000

Air pressure effects on biomass yield of two different Kluyveromyces strains.

The use of air pressure as a way of improving oxygen transfer in aerobic bioreactors was investigated. To compare the air pressure effects with traditional air bubbled cultures, experiments using a pressure reactor and a stirred flask, with the same oxygen transfer rate, were made. Kluyveromyces marxianus is an important industrial yeast and some of it show a "Kluyver effect" for lactose: even under oxygen limited growth conditions, certain disaccharides that support aerobic, respiratory growth, are not fermented. This study deals with the effect of increased pressure on the physiological behavior of two Kluyveromyces strains: K. marxianus ATCC10022 is a lactose-fermenting strain, whereas K. marxianus CBS 7894 has a Kluyver-effect for lactose. For K. marxianus ATCC10022 an air pressure increase of 2 bar led to a 3-fold increase in biomass yield. When air pressure increased an enhancement of ethanol oxidation of cell yeasts was also observed. Batch cultures of K. marxianus CBS 7894 exhibited different growth behaviour. Its metabolism was always oxidative and ethanol was never produced. With the increase in air pressure, it was possible to increase the productivity in biomass of K. marxianus CBS 7894. As a response to high oxygen concentrations, due to the increase in oxygen partial pressure, oxidative stress in the cells was also studied. Antioxidant defences, such as superoxide dismutase, catalase, and glutathione reductase, were at high activity levels, suggesting that these yeast strains could tolerate the increased pressures applied.

Journal Article↗

PubMed2000

Response of the thermophile Thermus sp. RQ-1 to hyperbaric air in batch and fed-batch cultivation.

The effects of increased air pressure in a culture of the thermophilic microorganism Thermus sp. RQ-1 were investigated. Cell growth dependence on oxygen supply was investigated in a fermenter at atmospheric pressure. Total oxygen depletion from the medium for low values of kLa was observed during the exponential growth phase. It was possible with this strain to enhance the oxygen transfer rate by increasing the air pressure. Cell productivity was improved by pressurisation up to 0.56 MPa for batch cultivation; and an induction of the antioxidant enzymes, superoxide dismutase and catalase, was observed with the rise in pressure. Cell pre-cultivation under pressurised conditions conferred to the cells more resistance to an exposure to hydrogen peroxide and more sensitivity to paraquat (methyl viologen). The usefulness of bioreactor pressurisation on the cultivation of Thermus sp. RQ-1 was demonstrated for fed-batch operation, with the attainment of higher cell densities. A two-fold increase in cell mass productivity was obtained by the use of hyperbaric air (0.5 MPa). With the pressurisation of the head-space in the reactor, it was also possible to eliminate the loss of liquid by evaporation, which amounted to more than 10% at 70 degrees C and atmospheric pressure.

Air Pressure↗

PubMed2000

Selective enzyme-mediated extraction of capsaicinoids and caratenoids from chili guajillo puya (Capsicum annum L.) using ethanol as solvent.

The selective extraction of capsaicinoids and carotenoids from chili guajillo "puya" flour was studied. When ethanol was used as solvent, 80% of capsaicinoids and 73% of carotenoids were extracted, representing an interesting alternative for the substitution of hexane in industrial processes. Additionally, when the flour was pretreated with enzymes that break the cell wall and then dried, extraction in ethanol increased to 11 and 7% for carotenoid and capsaicinoid, respectively. A selective two-stage extraction process after the treatment with enzymes is proposed. The first step uses 30% (v/v) ethanol and releases up to 60% of the initial capsaicinoids, and the second extraction step with industrial ethanol permits the recovery of 83% of carotenoids present in the flour.

Capsaicin↗

PubMed2000

Role of apoptosis signal-regulating kinase in regulation of the c-Jun N-terminal kinase pathway and apoptosis in sympathetic neurons.

We have previously shown that nerve growth factor (NGF) withdrawal-induced death requires the activity of the small GTP-binding protein Cdc42 and that overexpression of an active form of Cdc42 is sufficient to mediate neuronal apoptosis via activation of the c-Jun pathway. Recently, a new mitogen-activated protein (MAP) kinase kinase kinase, apoptosis signal-regulating kinase 1 (ASK1) which activates both the c-Jun N-terminal kinase (JNK) and p38 MAP kinase pathways and plays pivotal roles in tumor necrosis factor- and Fas-induced apoptosis, has been identified. Therefore, we investigated the role of ASK1 in neuronal apoptosis by using rat pheochromocytoma (PC12) neuronal cells and primary rat sympathetic neurons (SCGs). Overexpression of ASK1-DeltaN, a constitutively active mutant of ASK1, activated JNK and induced apoptosis in differentiated PC12 cells and SCG neurons. Moreover, in differentiated PC12 cells, NGF withdrawal induced a four- to fivefold increase in the activity of endogenous ASK1. Finally, expression of a kinase-inactive ASK1 significantly blocked both NGF withdrawal- and Cdc42-induced death and activation of c-jun. Taken together, these results demonstrate that ASK1 is a crucial element of NGF withdrawal-induced activation of the Cdc42-c-Jun pathway and neuronal apoptosis.

Animals↗

PubMed1999

Physiological responses of Tetrahymena pyriformis to copper, zinc, cycloheximide and Triton X-100.

Protozoa, and particularly ciliates, are essential in aerobic purification processes of wastewaters and have proved to be very sensitive to environmental changes. The physiological response of the ciliate Tetrahymena pyriformis was assessed in terms of mortality, growth and grazing capacity after exposure to four toxicants: copper, zinc, cycloheximide and Triton X-100. In the ranges of concentrations used, mortality, inhibition of growth and inhibition of grazing were observed with all toxicants employed, but in different ways. Copper and zinc showed lower toxicity than observed in other studies with protozoa, though some of the present results are in accordance with those reported by other authors. This supports the importance of the organism tested and the experimental conditions of the bioassays.

Journal Article↗

PubMed1999

Miniaturization and application of the MTT assay to evaluate metabolic activity of protozoa in the presence of toxicants.

This paper describes a critical evaluation of a miniaturised colorimetric assay, using MTT (3-[4,5-dimethyl-thiazol-2-yl]-2,5-diphenyl-tetrazolium bromide) reduction, applied to protozoan viability testing. The toxic substances used were copper, zinc, Triton X-100 (a membrane surfactant) and cycloheximide (an inhibitor of the protein synthesis). The viability assay of the ciliate protozoan Tetrahymena pyriformis was optimised in terms of MTT concentration and incubation time. Since protozoa are non adherent cells the MTT assay was modified in order to maintain the medium in the well. MTT proved to be effective in the measurement of Tetrahymena pyriformis viability. Four hours of MTT incubation followed by 30 minutes of incubation with DMSO were found to be the best incubation times for optical density reading. Furthermore, 10 mg/ml of MTT solution was the concentration that gave higher values of optical densities with minor medium interference.

Animals↗

PubMed1996

Flocculation onset, growth phase, and genealogical age in Saccharomyces cerevisiae.

Flocculation onset, the time during the fermentative cycle at which the strains of Saccharomyces cerevisiae become flocculent, is an important factor in the brewing industry. The flocculation ability of Flo 1 phenotype (strain NCYC 869) remained practically unchanged throughout the growth and seems to be insensitive to the presence of nutrients of the culture medium. On the contrary, the flocculation of NewFlo phenotype (strain NCYC 1195) exhibited a cyclic behaviour. It was found that the loss of flocculation in the early growth was the result of two combined effects: the dismantling of the flocculation mechanism of the cells coming from the inoculum and the nonflocculent state of the new cells produced after growth has started. The onset of flocculation of strain NCYC 1195 in the cultural conditions used in this work coincided with the end of the exponential growth, when the minimum glucose level in the culture medium was attained. It was demonstrated that it is possible to manipulate the flocculation onset by changing the initial glucose concentration in the culture medium.

Culture Media↗

PubMed1996

Freeze/thawing and sonication of Escherichia coli TB1 cells for cytochrome b5 recovery.

The influence of sonication power, suspension volume and cell concentration on the kinectics of cytochrome b5 and intracellular protein release by sonication of Escherichia coli TB1 cells was studied. The influence of freezing and thawing of the cell suspension was also evaluated. Freezing and thawing increased the recovery yield of cytochrome b5. The sonication efficiency increased with the increase of sonication power and with the decrease of the suspension volume and cell concentration.

Animals↗

PubMed1995

Effects of ethanol and acetic acid on the transport of malic acid and glucose in the yeast Schizosaccharomyces pombe: implications in wine deacidification.

Ethanol and acetic acid, at concentrations which may occur during wine-making, inhibited the transport of L-malic acid in Schizosaccharomyces pombe. The inhibition was non-competitive, the decrease of the maximum initial velocity following exponential kinetics. Glucose transport was not significantly affected either by ethanol (up to 13%, w/v) or by acetic acid (up to 1.5%, w/v). The uptake of labelled acetic acid followed simple diffusion kinetics, indicating that a carrier was not involved in its transport. Therefore, the undissociated acid appears to be the only form that enters the cells and is probably responsible for the toxic effects. Accordingly, deacidification by Ss. pombe during wine fermentation should take place before, rather than after, the main alcoholic fermentation by Saccharomyces cerevisiae.

Acetates↗

PubMed1995

Introduction of flocculation into industrial yeast, Saccharomyces cerevisiae saké, by protoplast fusion.

Protoplast fusion was applied to obtain intraspecific fusion in yeast strains in order to overcome restrictions imposed by the natural mating system. Acriflavine was used to construct petite mutants from non-flocculent industrial Saccharomyces cerevisiae saké strain. UV radiation was used to construct ura- mutants from a respiratory competent and highly flocculent S. cerevisiae NCYC869 strain. Fusion products were selected by complementation on minimal medium. The frequency of appearance of prototrophic hybrids was five per 10(5) protoplasts. The stable hybrids showed not only the S. cerevisiae saké characteristics but also flocculation ability, thereby confirming the success of the fusion.

Cell Fusion↗