Biological water denitrification—A review

Filamentous fungi are important organisms industrially and continue to attract research interest as microbiologists attempt to overcome the problems associated with their behavior in submerged culture. This review critically examines the literature describing these problems and where available suggests possible solutions to them. The influence of the chemical and physical environment on culture morphology, the process engineering challenges presented by different fungal morphologies, and the relationship between fungal morphology and metabolite production are all discussed.

Growth of filamentous fungi in submerged culture: problems and possible solutions

Succinic acid is of high interest as bio-feedstock for the chemical industry. It is a precursor for a variety of many other chemicals, e.g. 1,4-butandiol, tetrahydrofuran, biodegradable polymers and fumaric acid. Besides optimized production strains and fermentation processes it is indispensable to develop cost-saving and energy-effective downstream processes to compete with the current petrochemical production process. Various methods such as precipitation, sorption and ion exchange, electrodialysis, and liquid–liquid extraction have been investigated for the recovery of succinic acid from fermentation broth and are reviewed critically here.

Recovery of succinic acid from fermentation broth

This review sums up the activity in the field of in situ product removal in whole cell bioprocesses over the last 20 years. It gives a complete summary of ISPR operations with microbial cells and cites a series of interesting ISPR applications in plant and animal cell technology. All the ISPR projects with microbial cells are categorized according to their products, their ISPR techniques, and their applied configurations of the ISPR set-up. Research on ISPR application has primarily increased in the field of microbial production of aromas and organic acids such lactic acid over the last ten years. Apart from the field of de novo formation of bioproducts, ISPR is increasingly applied to microbial bioconversion processes. However, despite of the large number of microbial whole cell ISPR projects (approximately 250), very few processes have been transferred to an industrial scale. The proposed processes have mostly been too complex and consequently not cost effective. Therefore, this review emphasizes that the planning of a successful whole cell ISPR process should not only consider the choice of ISPR technique according to the physicochemical properties of the product, but also the potential configuration of the whole process set-up. Furthermore, additional process aspects, biological and legal constraint need to be considered from the very beginning for the design of an ISPR project. Finally, future trends of new, modified or improved ISPR techniques are given.

In situ product removal (ISPR) in whole cell biotechnology during the last twenty years.

Inexpensive fed-batch cultivation for high poly(3-hydroxybutyrate) production by a new isolate of Bacillus megaterium.

For the production of citric acid a four stage process consisting of the fermentation stage, extraction stage, reextraction stage and product stage has been tested. The present paper discusses the results of the extraction and the reextraction stage. Further a fermentation with recirculation of the fermentation broth after the product recovery is explained. The product recovery is achieved by a liquid–liquid extraction in a spray column.

Continuous production of citric acid with recirculation of the fermentation broth after product recovery

In a comprehensive study the properties of the reciprocating-jet-bioreactor have been investigated. Fermentations have been carried out with two fungi and one bacterium. The fungi were Cyathus striatus for the production of antibiotics and Aspergillus niger for the production of citric acid. The bacterium Zymomonas mobilis was used in an anaerobic fermentation for the production of ethanol. The reciprocating-jet-bioreactor showed excellent properties as fermenter, especially when the biosuspension is highly viscous and non-Newtonian by nature.

Growth of fungi and bacteria in the reciprocating jet bioreactor

Concept of separation of stages coupled with novel design of reciprocating jet bioreactor have been incorporated in this research for the development of high efficiency treatment system for contaminated wastewaters.

Nitrification and denitrification in a system of reciprocating jet bioreactor

The development and investigation of high-efficiency bioreactors is one of the primary problems bioprocess engineers have to solve. With increasing efficiency of the bioreactor the downstream processes will be much simplified, energy and costs will be substantially reduced.

Development and efficiency of a new generation of bioreactors

In a two-stage pilot plant biological processes effect substantial degradation of organic carbon compounds and the ammonium contained in highly contaminated waste waters at extremely short mean residence time in the bioreactor. This achievement is mainly due to employment of a newly-developed type of bioreactor — the reciprocating jet bioreactor.

H. Brauer

Papers

Continuous production of citric acid with recirculation of the fermentation broth after product recovery

Growth of fungi and bacteria in the reciprocating jet bioreactor

Nitrification and denitrification in a system of reciprocating jet bioreactor

Development and efficiency of a new generation of bioreactors

Aerobic two-stage biological degradation of organic carbon compounds and ammonium