Efficient leaching of cellulases produced by Trichoderma harzianum in solid state fermentation

Recovery of cellulases from solid state culture of #Trichoderma harzianum$ was efficiently achieved by hydraulic pressing. Pressing of fermented solids yielded carboxymethyl-cellulase (CMCase) extraction efficiency of 71% and a ratio of leachate to fermented solids of 0.58 (v/w). Addition of water to pressed solids and second pressing improved the efficiency (95%) with simultaneous increase in the ratio to 1.16 (v/w). The overall extraction of filter paper activity was lower (85%) than that of CMCase. This technique is simple and its extraction efficiency is similar to that obtained in multiple-contact counter-current systems. The hydraulic press in its individuality was not used earlier to leach the product from fermented solids. (Résumé d'auteur

Pectinase-hyperproducing mutants of Aspergillus niger C28B25 for solid-state fermentation of coffee pulp

The aim of this study was to improve mold strains for the production of pectinases by solid-state fermentation (SSF) of coffee pulp. A screening of 248 strains, isolated in Mexico's coffee-growing areas, permitted us to select a wild strain of #Aspergillus niger$ which in 72 h attains a peak production of 27.7 U ml-1(138 U g-1 dry pulp) of pectinase measured by viscosimetry. Though the use of a selective culture medium with low water activity (aw = 0.954) with 2-deoxy-glucose (2DG) it was possible to isolate pectinase-hyperproductive mutant strains for SSF(44.5 U ml-1, 228 U g-1 dry pulp). Derepressed mutant strains that hyperproduced pectinase by submerged fermentation (SmF) were also obtained using a classic selective medium with high water activity (pectin + 2DG) with aw = 0.999. A comparison between both classes of mutants, called AW96 and AW99, respectively, points out the need to design special selective media in order to obtain strains adapted either to SSF or Smf in which the aw level would be a key selecting factor. (Résumé d'auteur

Potential of using a single fermenter for biomass build-up, starch hydrolysis, and ethanol production

Data on conversion of starch on biomass and ethanol by #Schwanniomyces castellii in an aerobic-anaerobic solid state fermentation is reported. #Schwanniomyces castellii grew exponentially in the aerobic phase (12h) and simultaneously hydrolyzed nearly half (55%) of the starch initially present. The accumulation of glucose increased up to 12h, whereas maltose was nearly absent beyond 7h. Shift or metabolism from oxidative to fermentative pattern was observed about 10h as a result of the build-up of CO2 level and faster utilization of O2. The ethanol production in the anaerobic phase reached the level of 89.3 mg ethanol/g initial dry matter by the end of 30h. A total of 92.9% of the starch is utilized during the fermentation. The overall ethanol conversion yields are 57.8% of the theoretical value, whereas in the anaerobic phase it was found to be 94.4%. The cell shape, its morphology, and the type of attachment to the solid support were found to be similar in aerobic and anaerobic phases of fermentation. Data given in this work indicate the feasibility of using one single fermenter for aerobic growth to generate inoculum as well as to simultaneously hydrolyze the starch and subsequent anaerobic fermentation to produce ethanol. (Résumé d'auteur

Potential of ensiling for efficient management of spent residue from solid state fermentation system

Studies on ensiling of spent solids from solid state fermentation process for production of cellulases by #Trichoderma harzianum$ showed that good quality ensiled solids can be obtained by using about 43% initial substrate dry matter with 0.3% ensiling additive. (Résumé d'auteur

Maintenance of heat and water balances as a scale-up criterion for the production of ethanol by Schwanniomyces castellii in a solid state fermentation system

The scale-up of column fermenters by 6 to 410 gravimetric scale factors, from 10 g moist substrate size, has been achieved efficiently by maintaining heat and water balances in the media. The data on the patterns of ethanol production, biomass formation, the concentration of different carbohydrates, dry matter and pH values against time were of equal magnitude in 10- and 60-g size column fermenters. The reactors of 60-, 370- and 4100-g sizes also compared well in respect of O2 consumption, CO2 evolution and the specific growth rates in aerobic and anaerobic fermentations phases. The overall productivities of ethanol were similar in all the four column fermenters. The ability to obtain the same results in all the fermenter sizes, in spite of the increases in the diameter and the height of the columns, indicates the high potential of this simple scale-up criterion which has not been used earlier for scale-up of any fermentation process. (Résumé d'auteur

Quantitative full-colour transmitted light microscopy and dyes for concentration mapping and measurement of diffusion coefficients in microfluidic architectures

International audienceA simple and versatile methodology has been developed for the simultaneous measurement of multiple concentration profiles of colourants in transparent microfluidic systems, using a conventional transmitted light microscope, a digital colour (RGB) camera and numerical image processing combined with multicomponent analysis. Rigorous application of the Beer-Lambert law would require monochromatic probe conditions, but in spite of the broad spectral bandwidths of the three colour channels of the camera, a linear relation between the measured optical density and dye concentration is established under certain conditions. An optimised collection of dye solutions for the quantitative optical microscopic characterisation of microfluidic devices is proposed. Using the methodology for optical concentration measurement we then implement and validate a simplified and robust method for the microfluidic measurement of diffusion coefficients using an H-filter architecture. It consists of measuring the ratio of the concentrations of the two output channels of the H-filter. It enables facile determination of the diffusion coefficient, even for non-fluorescent molecules and nanoparticles, and is compatible with non-optical detection of the analyte

High-accuracy mass determination of neutron-rich rubidium and strontiumiIsotopes

The penning-trap mass spectrometer ISOLTRAP, installed at the on-line isotope separator ISOLDE at CERN, has been used to measure atomic masses of $^{88,89,90m,91,92,93,94}$Rb and $^{91- 95}$Sr. Using a resolving power of R $\!\scriptstyle\approx$1 million a mass accuracy of typically 10 keV was achieved for all nuclides. Discrepancies with older data are analyzed and discussed, leading to corrections to those data. Together with the present ISOLTRAP data these corrected data have been used in the general mass adjustment