Mohamad Aji Ikhrami1, Jaka Widada2, Indun Dewi Puspita1 and Masagus Muhammad
Prima Putra1*
1Fish Product Technology, Department of Fisheries, Faculty of Agriculture, Universitas Gadjah
Mada, Jl. Flora gedung A4, Bulaksumur Yogyakarta 55281
2Department of Agricultural Microbiology, Faculty of Agriculture, Universitas Gadjah Mada, Jl.
Flora gedung A4, Bulaksumur Yogyakarta 55281
*Corresponding author, e-mail: primaputra@ugm.ac.id
ABSTRACT
Streptomyces is a Gram-positive bacteria that produces the largest secondary metabolite
compounds. The results of whole-genome sequence analysis showed that Streptomyces can carry
more than 30 Biosynthetic Gene Clusters (BGC) encoding secondary metabolites that have the
potential to be explored in the exploration for new bioactive compounds. However, not all BGC
can be expressed in the laboratory scale and requires a specific activation method. This study aims
to explore the potential of chitosan as an elicitor compound to activate and or increase the
antibacterial activity of Streptomyces sp. GMR-22 was tested against histamine-producing bacteria
(HPB) Morganella morganii TK7 and Citrobacter freundii CK1. Chitosan was added to the
fermentation medium with the final concentration of 250, 500, and 750 μg/ml while without the
addition of chitosan used as control. Fermentation was carried out for 10 days at room temperature,
with constant agitation 200 rpm. The supernatant was separated by centrifugation at 3500 rpm for
15 minutes, then fractionation with ethyl acetate, concentrated by vacuum rotary evaporator, and
freeze-dried. The test for antibacterial activity was carried out by the microdilution method with
an extract concentration of 100 mg/ml. The test results of the microdilution method showed that
the addition of chitosan successfully increases the antibacterial activity with the highest activity
shown by the water fraction of 250 μg/ml addition of chitosan which is effective in inhibiting the
growth of Morganella morganii TK7 and Citrobacter freundii CK1 by 97,29% and 97,92%
respectively.
Keywords: antibacterial, histamine-forming bacteria, elicitor, chitosan, Streptomyces sp. GMR-
22
