Abstract:In Malaysia black pod disease caused by Phytophthora palmivora is one of the serious problems causing yield loss in cocoa plantation. In this study, an endophytic bacterium living within tissues of healthy Theobroma cacao L. leaves was isolated and assessed its ability to inhibit the growth of P. palmivora. Based on molecular identification using 16S rDNA gene sequences analysis, this endophytic bacterium was identified as Bacillus amyloliquefaciens which was subsequently named as Bacillus amyloliquefaciens LKM-UL. Preliminary test using dual culture method showed B. amyloliquefaciens LKM-UL has strong ability to inhibit the growth of P. palmivora. B. amyloliquefaciens showed the highest antifungal activity after 24 h incubation in nutrient broth. Cells-free supernatant from B. amyloliquefaciens showed the highest antifungal activity of 30.6 mm with cell concentration of Log 10 10.63 CFU/mL via agar disc diffusion method. B. amyloliquefaciens LKM-UL also produced plant growth hormone identified as 1-naphthalene acetic acid (NAA), tryptamine, 3-indole propionic acid (IPA), indole-3-butyric acid (IBA), gibberellic acid (GA), trans-zeatin and kinetin.
Polyhydroxyalkanoates (PHA) are bioplastics, produced by various bacteria as food and energy reservoir. PHA is an alternative for synthetic plastic because they are environmentally friendly and can be degraded naturally by microorganisms. One of the important factors for the growth of PHA producing bacteria is an excess of carbon supply. In order to reduce the overall cost of PHA production, a low cost pure substrate, which is cocoa pod husks (CPH) was used as a carbon source. The objectives of this study were to isolate and screen PHA producing bacteria from landfill samples which are leachate and soil, to identify the PHA producing bacteria by using morphological characterization and 16s rDNA gene sequencing and to determine the best percentage of CPH that can be used as a carbon source for PHA producing bacteria. PHA producing bacteria from leachate and soil from landfill in Jeram, Selangor were screened by using Nile Blue A staining method. Two potential PHA producers with the brightest fluorescence under UV light from each samples were isolated and characterized by using morphological and molecular identification. Results of morphological identification shows all bacterial isolates have a rod shape and have a capsule, three bacterial isolates (L4, S3, S5) have an endospore while the remaining does not have endospore (L1). Three out of four were Gram positive bacteria (L4, S3, S5) and the remaining was Gram negative bacteria (L1). These isolates were confirmed of their identity as K. pneumoniae (L1), B. cereus (L4 & S3) and B. toyonensis (S5) using 16s rDNA gene sequencing. Different concentration of CPH, which are 2% (w/v), 5% (w/v), 7% (w/v) and 10% (w/v) were used to study the best percentage of CPH that can be used as carbon source. PHA accumulation was the highest at 7% (w/v) for all bacterial species tested and lowest at 10% (w/v) CPH except for B. toyonensis. Therefore, K. pneumoniae, B. cereus and B. toyonensis which isolated from landfill show the ability to produce PHA and the used of 7% (w/v) cocoa pod husks as carbon source give the highest PHA accumulation.
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