Abstract
BackgroundActinomycetes are saprophytic soil bacteria, and a rich source of industrial enzymes. While some of these enzymes can be produced using well-characterized production platforms such as Escherichia coli or Bacillus subtilis,Streptomyces lividans may be the preferred host for proper folding and efficient secretion of active enzymes. A combination of promoters, signal peptides and hosts were tested in order to obtain the best protein expression in this actinomycete. The xylanase, Xys1, from S. halstedii, the α-amylase, Amy, from S. griseus and the small laccase, SLAC, from S. coelicolor were used as reporters.ResultsThe promoters xysAp from S. halstedii JM8 and pstSp from S. lividans were the most efficient among those tested. An improvement of 17 % was obtained in xylanase activity when the signal peptide of the α-amylase protein (Amy) of S. griseus IMRU3570 was used to direct its secretion. Enhanced expression of SsgA, a protein that plays a role in processes that require cell-wall remodelling, resulted in a improvement of 40 and 70 % of xylanase and amylase production, respectively. Deletion of genes SLI7232 and SLI4452 encoding putative repressors of xysAp provided improvement of production up to 70 % in the SLI7232 deletion strain. However, full derepression of this promoter activity was not obtained under the conditions assayed.ConclusionsStreptomyces lividans is a frequently used platform for industrial enzyme production and a rational strain-development approach delivered significant improvement of protein production by this host.Electronic supplementary materialThe online version of this article (doi:10.1186/s12934-016-0425-7) contains supplementary material, which is available to authorized users.
Highlights
Actinomycetes are saprophytic soil bacteria, and a rich source of industrial enzymes
Escherichia coli has usually been a preferred host for protein production, for reasons of high expression levels and short fermentation time
We show that selection of strong promoters, modification of signal peptides and use of different S. lividans hosts result in improved production of putative industrial proteins such as the xylanase Xys1 from S. halstedii JM8, the α-amylase Amy from S. griseus IMRU3570 and the small laccase S. griseus and laccase (SLAC) from S. coelicolor
Summary
Actinomycetes are saprophytic soil bacteria, and a rich source of industrial enzymes. While some of these enzymes can be produced using well-characterized production platforms such as Escherichia coli or Bacillus subtilis, Streptomyces lividans may be the preferred host for proper folding and efficient secretion of active enzymes. Frequently insoluble inclusion bodies are formed, which frustrates downstream processing [1,2,3] In such cases, alternative production platforms are required, and microorganisms of the genus Streptomyces have been successfully applied as a good alternative expression platform for heterologous protein production [4,5,6,7,8,9,10]. Enhanced fragmentation of the mycelia has a major impact on growth and product
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