Search

Corynebacterium glutamicum(C. glutamicum) is a highly promising alternative prokaryotic host for recombinant protein expression, as it possesses several significant advantages overEscherichia coli (E. coli), the currently leading bacterial protein expression system. During the past decades, several experimental techniques and vector components for genetic manipulation ofC. glutamicumhave been developed and validated, including strong promoters for tightly regulating target gene expression, various types of plasmid vectors, protein secretion systems and methods of genetically modifying the host strain genome to improve protein production potential. This review critically discusses current progress in establishingC. glutamicumas a host for recombinant protein expression, and examines, in depth, some successful case studies of actual application of this expression system. The established “expression tool box” for developing novel constructs based onC. glutamicumas a host are also evaluated. Finally, the existing issues and solutions in process development withC. glutamicumas a host are specifically addressed. [ABSTRACT FROM PUBLISHER]

There is considerable interest in exploiting the novel physical and biological properties of microbial exopolysaccharides in industry and medicine. For economic and scientific reasons, large scale production under carefully monitored and controlled conditions is required. Producing exopolysaccharides in industrial fermenters poses several complex bioengineering and microbiological challenges relating primarily to the very high viscosities of such culture media, which are often exacerbated by the producing organism''s morphology. What these problems are, and the strategies for dealing with them are discussed critically in this review, using pullulan, curdlan, xanthan, and fungal ββ-glucans as examples of industrially produced microbial exopolysaccharides. The role of fermenter configuration in their production is also examined. [ABSTRACT FROM AUTHOR]

It has been known for many years that oxygen (O2) may have toxic effects on aerobically growing microorganisms, mainly due to the threat arising from reactive oxygen species (ROS). In submerged culture industrial fermentation processes, maintenance of adequate levels of O2 (usually measured as dissolved oxygen tension (DOT)) can often be critical to the success of the manufacturing process. In viscous cultures of filamentous cultures, actively respiring, supplying adequate levels of O2 to the cultures by conventional air sparging is difficult and various strategies have been adopted to improve or enhance O2 transfer. However, adoption of those strategies to maintain adequate levels of DOT, that is, to avoid O2 limitation, may expose the fungi to potential oxidative damage caused by enhanced flux through the respiratory system. In the past, there have been numerous studies investigating the effects of DOT on fungal bioprocesses. Generally, in these studies moderately enhanced levels of O2 supply resulted in improvement in growth, product formation and acceptable morphological changes, while the negative impact of higher levels of DOT on morphology and product synthesis were generally assumed to be a consequence of "oxidative stress." However, very little research has actually been focused on investigation of this implicit link, and the mechanisms by which such effects might be mediated within industrial fungal processes. To elucidate this neglected topic, this review first surveys the basic knowledge of the chemistry of ROS, defensive systems in fungi and the effects of DOT on fungal growth, metabolism and morphology. The physiological responses of fungal cells to oxidative stress imposed by artificial and endogenous stressors are then critically reviewed. It is clear that fungi have a range of methods available to minimize the negative impacts of elevated ROS, but also that development of the... [ABSTRACT FROM AUTHOR]

Organisms of the genus Gluconobacter have been widely utilized within the biotechnology industry for many decades, due to their unique metabolic characteristics. The metabolic features that render Gluconobacter so useful in biotransformation processes, vitamin synthesis, and, as the biological element in sensor systems, are critically evaluated, and the relevance of recent biochemical genetic studies to current and future industrial Gluconobacter processes is discussed. The impact of recombinant gene technology on the status of Gluconobacter processes and the potential use of such techniques in clarifying aspectsof the physiology of Gluconobacteris reviewed. [ABSTRACT FROM AUTHOR]