Continuous citric acid production by immobilized aspergillus niger: reactor performance and fermentation kinetics

Efficient production of citric acid in segmented fermentation using Aspergillus niger based on recycling of a pellet-dispersion strategy

Segmentation recycling fermentation based on a pellet-dispersion strategy to reconstruct the traditional citric acid batch fermentation process is reported.

Citric acid fermentation by magnetic drum contactor: Use of methanol and ethanol for higher production

Use of methanol or ethanol in the magneto-biotechnological technique was found to be enhance citric acid production in a magnetic drum contactor operation with Aspergillus niger AJ 117173. Continuous and repeated-batch fermentations were conducted with the addition of 2% ethanol. Continuous fermentation for 50 d gave a better citric acid yield (85%) and average productivity (3.8 g.l(-1).d(-1)) than repeated-batch fermentation over 60 d (65%, 2.3 g.l(-1).d(-1)).

Food bioconversions and metabolite production using immobilized cell technology

This review explores recent advances in the use of immobilized cells for the production of metabolites used in the food industry, such as enzymes, amino acids, organic acids, alcohols, aroma compounds, polysaccharides, and pigments. Some food bioconversions such as fermentation of soy sauce and various hydrolysis are also considered. Special emphasis was placed on existing or potential industrial processes. This article also reports the effects of the reactor (configuration and working conditions), the immobilized cell physiological status (growing, nongrowing, or permeabilized), and of the carrier type, configuration, and size on the performance of immobilized cell systems. Compared with free cell fermentation, the main advantage of using immobilized cells is an increase in productivity, particularly in the case of continuous fermentation. For monoenzymatic reactions, nongrowing immobilized cells are often reported to exhibit a higher stability than free or immobilized enzymes.

Continuous itaconic acid production by immobilized biocatalysts

The continuous itaconic acid production from sucrose with Aspergillus terreus TKK 200-5-3 mycelium immobilized on polyurethane foam cubes was optimized in column bioreactors using statistical experimental design and empirical modelling. The highest itaconic acid product concentration calculated on the basis of the obtained model was 15.8 g l-1 in the investigated experimental area, when sucrose concentration was 13.5%, aeration rate 150 ml min-1 and residence time 178 h. From sucrose with immobilized A. terreus TKK 200-5-3 mycelium itaconic acid production was stable for at least 4.5 months in continuous column bioreactors. In comparison, using glucose as substrate and immobilized A. terreus TKK 200-5-1 mycelium as biocatalyst similar stability was obtained with higher product concentration. The omission of copper sulphate from the production medium gave the highest itaconic acid product concentration (26 g l-1) from 9% glucose with 0.25% ammonium nitrate and 0.095% magnesium sulphate.