BackgroundCollagen has proved valuable as biomedical materials for a range of clinical applications, particularly in wound healing. It is normally produced from animal sources, such as from bovines, but concerns have emerged over transmission of diseases. Recombinant collagens would be preferable, but are difficult to produce. Recently, studies have shown that ‘collagens’ from bacteria, including Streptococcus pyogenes, can be produced in the laboratory as recombinant products, and that these are biocompatible. In the present study we have established that examples of bacterial collagens can be produced in a bioreactor with high yields providing proof of manufacture of this important group of proteins.ResultsProduction trials in shake flask cultures gave low yields of recombinant product, < 1 g/L. Increased yields, of around 1 g/L, were obtained when the shake flask process was transferred to a stirred tank bioreactor, and the yield was further enhanced to around 10 g/L by implementation of a high cell density fed-batch process and the use of suitably formulated fully defined media. Similar yields were obtained with 2 different constructs, one containing an introduced heparin binding domain. The best yields, of up to 19 g/L were obtained using this high cell density strategy, with an extended 24 h production time.ConclusionsThese data have shown that recombinant bacterial collagen from S. pyogenes, can be produced in sufficient yield by a scalable microbial production process to give commercially acceptable yields for broad use in biomedical applications.

Recently, a different class of collagen-like molecules has been identified in numerous bacteria. Initial studies have shown that these collagens are readily produced in E. coli and they have been isolated and purified by various small scale chromatography approaches. These collagens are non-cytotoxic, non immunogenic and can be produced in much higher yields than mammalian collagens, making them potential new collagens for biomedical materials. One of the major drawbacks with large scale fermentation of collagens has been appropriate scalable down-steam processing technologies. Like other collagens, the triple helical-domains of bacterial collagens are particularly resistant to proteolysis. The present study describes the development and optimisation of a simple, scalable procedure using a combination of acid precipitation of the E. coli host proteins, followed by proteolysis of residual host proteins to produce purified collagens in large scale without the use of chromatographic methods.

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