Genetic improvement of Bacillus licheniformis strains for efficient deproteinization of shrimp shells and production of high-molecular-mass chitin and chitosan.
By targeted deletion of the polyglutamate operon (pga) in Bacillus licheniformis F11, a derivative form, F11.1 (Δpga), was obtained that, along with lacking polyglutamate (PGA) formation, displayed enhanced proteolytic activities. The phenotypic properties were maintained in a strain in which the chiBA operon was additionally deleted: F11.4 (ΔchiBA Δpga). These genetically modified strains, carrying the Δpga deletion either alone (F11.1) or together with the ΔchiBA (F11.4) deletion, were used in fermentations (20-liter scale) aiming at the deproteinization of shrimp shells in order to obtain long-chain chitin. After chemical deacetylation, the resulting chitosan samples were analyzed by nuclear magnetic resonance spectroscopy, size exclusion chromatography, and viscometry and compared to a chitosan preparation that was produced in parallel by chemical methods by a commercial chitosan supplier (GSRmbH). Though faint lipid impurities were present in the fermented polysaccharides, the viscosity of the material produced with the double-deletion mutant F11.4 (Δpga ΔchiBA) was higher than that of the chemically produced and commercially available samples (Cognis GmbH). Thus, enhanced proteolytic activities and a lack of chitinase activity render the double mutant F11.4 a powerful tool for the production of long-chain chitosan.
Westfälische Wilhelms-Universität Münster, Institut für Molekulare Mikrobiologie und Biotechnologie, D-48149 Münster, Germany.
Kerstin
K
Hoffmann
Gabriele
G
Daum
Marina
M
Köster
Werner-Michael
WM
Kulicke
Heike
H
Meyer-Rammes
Bernward
B
Bisping
Friedhelm
F
Meinhardt
D000818:Animals; D001407:Bacillus / Q000235:genetics* / Q000378:metabolism*; D002686:Chitin / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D048271:Chitosan / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D002850:Chromatography, Gel; D005798:Genes, Bacterial; D008055:Lipids / Q000032:analysis; D008970:Molecular Weight; D030781:Organisms, Genetically Modified / Q000235:genetics / Q000378:metabolism; D033561:Penaeidae / Q000382:microbiology*; D011099:Polyglutamic Acid / Q000378:metabolism; D017384:Sequence Deletion
D008055:Lipids; D002686:Chitin; D011099:Polyglutamic Acid; D048271:Chitosan