Potential of syncephalastrum racemosum and rhizopus arrhizus isolated from oil palm trunks produce chitosans that inhibit the growth of ganoderma boninense

Abstract

Chitosan has been proposed as a treatment to suppress Ganoderma infection on oil palm. Syncephalastrum racemosum and Rhizopus arrhizus, growing on oil palm trunk, were examined on their ability to produce chitosan. Chitinous materials from both fungi were deproteinised and deacetylated using different concentrations of sodium hydroxide (NaOH). Chitosans from R. arrhizus (FuCsRa), S. racemosum (FuCsSr) were compared with crab shells’ chitosan (CrCs) through the Fourier-transform infrared spectroscopy (FTIR) analysis. The deacetylation degrees of different chitosan sources were also determined. FTIR analysis showed that chitosans produced by these fungi and crab shell’s chitosan had a similar pattern of FTIR spectrum, but differed in their deacetylation degrees. The next experiment examined the ability of these chitosans to suppress the growth of Ganoderma boninense (G. boninense) in vitro. The experiment consisted of 11 treatments: controls, media with CrCs (at 5000, 7500, 10 000 ppm), media with FuCsRa (at 5000, 7500, 10 000 ppm), media with FuCsSr (at 5000, 7500, 10 000 ppm) and antagonistic test (S. racemosum; R. arrhizus). The results showed that CrCS at 5000, 7500 and 10 000 ppm enhanced the growth of G. boninense. A concentration of 10 000 ppm of CrCs nearly doubled the growth of Ganoderma compared to control. FuCsSc inhibited the growth of G. boninense at all concentrations from -28% to 31% compared to control. The in vitro antagonistic effect of S. racemosum showed a high effect at inhibiting the growth of G. boninense (-43% compared to control). This in vitro study demonstrated the ability of chitosan extracted from fungi growing on oil palm trunks to suppress Ganoderma growth. CLE IN PRE