Bacillus as Expression Hosts

Contributed by Darwin Bandoy, DVM

This particular talk by (Bill Widner, Ph.D., Novozymes Staff Scientist) tantalized my interest as I only associate Bacillus with things a veterinarian must know to avoid, which is Bacillus anthracis, a deadly disease causing gram-positive bacteria in animals and humans particularly in ruminants. Anthrax gained notoriety recently in the PhDUS when letters post 9/11 were mailed to media and congressional offices. So with all this negative association with Bacillus, what makes it a good expression host? Bacillusare strong secretors and the speaker had prior experience with this working with Bacillus thurigiensis that secrete crystal proteins with insecticidal properties for microbiology. Bacillus is also cheap to grow, does not have the endotoxin of E. coli, and without much intellectual property barrier. Putting this together makesBacillus an attractive expression host. But if you have a good expression host, how do you make things better? Technologies to improve production strains include developing stronger promoters, knocking protease activity, overexpressing chaperones and increasing copy numbers.

What is the path to the product using Bacillus as expression host? A new products is first identified, the cloning of the gene product is performed, followed by construction of expression cassettes and introduction intro various bacillus host. But it is not enough for Bacillusto to express it, it must do so on a larger scale. This is done sequentially from lab scale (2 L) fermenters for yield optimization to pilot plant level (500 to 2000 L) and full scale production. Novozymes core technologies in genomics are used for quality control. Experimentation is unavoidable as some genes are expressed better in one Bacillusthan the other. Even within a given species, some isolates are better expressors than others. This lecture on using Bacillus reminds of the Star Wars quote by Luke Skywalker, “there is good in him”, as though the Bacillusgenera contains pathogens that secrete toxins, that secreting capability can be harnessed for good purposes.

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