M. Mota

Detection and quantification of long chain fatty acids in liquid and solid samples and its relevance to understand anaerobic digestion of lipids

A method for long chain fatty acids (LCFA) extraction, identification and further quantification by gas chromatography was developed and its application to liquid and solid samples collected from anaerobic digesters was demonstrated. After validation, the usefulness of this method was demonstrated in a cow manure digester receiving pulses of an industrial effluent containing high lipid content. From the LCFA analysis data it was showed that the conversion of oleic acid, the main LCFA fed to the reactor, by the adapted biomass became faster and more effective along the successive pulses. Conversely, the accumulation of palmitic acid in the solid phase suggests that degradation of this LCFA, under these conditions, is less effective.

Yarrowia lipolytica lipase production enhanced by increased air pressure

Aims:  To study the cellular growth and morphology of Yarrowia lipolytica W29 and its lipase and protease production under increased air pressures.

Influence of physico-chemical properties of porous microcarriers on the adhesion of an anaerobic consortium

The ability for biomass colonization of four porous mineral microcarriers (sepiolite, clay, pozzolana and foam glass-Poraver), was studied and related to their surface properties. The surface hydrophobicity of the mineral carriers was a more important factor influencing colonization by the anaerobic consortium than was surface charge. It was possible to correlate linearly the degree of hydrophobicity with the biomass retention capacity. Although the thermodynamic theory did not explain adhesion, an increase in cell attachment was directly related to the decrease of the positive values of the free energy of adhesion. Surface roughness, porosity and the amount of surface Mg2+, were also determinant factors in bacterial immobilization. However a great biomass accumulation can originate a decrease in biological activity due to mass transfer limitations. Journal of Industrial Microbiology & Biotechnology (2000) 24, 181–186.

Microbial and operational response of an anaerobic fixed bed digester to oleic acid overloads

The effect of oleic acid overloads on biomass accumulation and activity in an anaerobic filter was investigated. An anaerobic fixed-bed reactor specially designed to allow the regular withdrawal of accumulated biomass was used for that purpose. Organic and hydraulic shocks were performed during four days, by stepwise increasing the substrate concentration from 4000 to 20 000 mg COD/l or by reducing the hydraulic retention time from 16 to 3.2 h. During the organic shock, operational performance was more affected than in the hydraulic one, which was the result of the higher degree of inhibition detected in the acetoclastic, hydrogenophilic and syntrophic activities. The ratio adhered/total biomass remained between 17 and 32% during the hydraulic shock, and between 13 and 60% during the organic shock, suggesting a more stable biofilm during the hydraulic shock. A long time (900 h) after the hydraulic shock, hydrogenophilic and syntrophic activities recovered to higher values than before the shock, but after the organic shock only acetoclastic activity recovered pre-shock values. Hydraulic shock induced an increase in tolerance to oleic acid toxicity, evidenced by an increase in the toxicity limit (IC50) from 140 30 to 215 25 mg/l.

Optimization study of Escherichia coli TB1 cell disruption for cytochrome b5 recovery in a small-scale bead mill

The recovery of a recombinant intracellular protein, cytochrome b5, from Escherichia coli TB1 cells was carried out by bead mill disintegration in a discontinuous small‐scale instrument. This process was optimized by the use of experimental factorial design. Several parameters were studied: operating time, amount and size of beads, cellular suspension concentration, and presence of toluene and lysozyme. For the experimental conditions used, only the time of treatment and bead load had significant effects. The optimal values of these variables were found by applying the response surface methodology.

Influence of up-flow velocity on the performance of an anaerobic filter under oleic acid overloads

An upflow velocity of 0.21 m h−1 was optimal to minimize the effect of organic shocks (from 6 to 30 kg COD m−3 d−1) when operating an upflow anaerobic filter for the treatment of an oleic acid-based effluent (50% w/v COD). This value represented the transition between a mass transfer controlled regime and a kinetic regime. Under hydraulic shock loads, an increase in upflow velocity from 0.3 to 0.4m h−1 decreased the removal efficiency from 68 to 51%.

Doppler spectroscopy of blood in capillary plexus under the action of 40% glucose solution

The investigation of blood dynamical characteristics in the skin under the action of 40% glucose solution was performed in vivo by the laser Doppler technique. Experiments demonstrate that glucose solution affects significantly the blood perfusion and concentration. Qualitative explanation was made for observed perfusion dynamic effect in the skin dermis based on the following factors: tissue cells shrinkage and additional capillaries opening under osmotic stress. The size of glucose vesicle lens was measured under the skin by ultrasonography. The analysis of vesicle sizes monitoring leads to the conclusion that glucose lens spread, basically, along the skin than in the perpendicular to the skin surface direction. Obtained results show the significant anisotropic perturbation of the dynamic characteristics of blood in vascular plexus under the optical active solution influence that must be taken into consideration during optical clarification of biological tissues.