RESUMO
Aspergillus niger ATCC 9142 mycelium was entrapped in calcium alginate beads and employed in an air-lift completely stirred reactor for continuous production of citric acid. Maximum yield obtained from 10% (w/v) sucrose was 12 g dm(-3) with about 40% fermentation efficiency. Maximum rate of production 70 mg g(-1) h(-1) was about five times that obtained in classical batch fermentation.
RESUMO
A direct cell size measurement technique and an image analysis based sizing method were developed. The former consisted of a manual size measurement of the two-dimensional cell images on a video screen, with automatic data recording. This method was chosen as the reference. The latter, a semiautomatic method took advantage of a commercial computer program designed for image processing and particle morphology analysis. It gave average and median size values which were compatible with the manual method. However, the performance of these time consuming methods is limited. Hence, the laser granulometry technique, intrinsically far more powerful while capable of analysing millions of sample objects in a short time delay, was applied. The comparison revealed that this method gives too low size values, particularly in disagreement with the known dimensions of the bacterial (Zymomonas mobilis) cells. A size correction method was developed to realign the granulometry results of Z mobilis cell samples with those of the direct manual measurement method.
Assuntos
Bactérias/citologia , Técnicas Bacteriológicas , Processamento de Imagem Assistida por Computador/métodos , Micologia/métodos , Saccharomyces cerevisiae/citologia , Fermentação , Lasers , Fotomicrografia , Refratometria , Espalhamento de Radiação , Zymomonas/citologiaRESUMO
Comparison of three different cell viability methods: slide count, plate count and methylene blue staining techniques, applied on Zymomonas mobilis cultures, was performed. The slide technique proved to be faster and more accurate than the plate count method, and both of them far more reliable than the standard methylene blue method which constantly overestimated the Zymomonas cell viability. The slide technique is advantageous also because it gives information on the cell morphology changes, notably the abnormal cell elongation, in the ethanol fermentation.