Pusat Pengajian Sains Kajihayat - Tesis

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Evaluation On Pathogenicity Of Entomopathogenic Fungi Metarhizium Anisopliae On The Rove Beetle, Paederus Fuscipes Curtis
(2018-12)
Tan, Andy Fu Hao
Rove beetle, Paederusjuscipes Curtis is a natural predator of several crop pests in agricultural ecosystem, however their high intrusion into human settlements causes them to become a public health concern due to Paedarus dermatitis infection among human. This study was undertaken to investigate the effectiveness of Metarhizium anisopliae fungi as a biocontrol agent for P. fuscipes, The pathogenicity of entomopathogenic fungi, Metarhizium anisopliae against the beetle P. fuscipes were tested using three teclmiques; soil infection, bait infection, and horizontal transmission via endo-cannibalistic behaviour.
Characterisation And Pathogenicity Of Fungi Causing Sooty Blotch And Flyspeck (Sbfs) Disease Of Mango (Mangifera Indica L.) In Peninsular Malaysia
(2024-09)
Tham, Khai Xin
The sooty blotch and flyspeck (SBFS) disease complex, caused by multiple fungal species, leads to black smudges and clusters of black spots on various fruits, including mango, impacting their marketability as fresh fruit. Although not previously reported in Malaysia, field visits in 2018 found similar SBFS disease symptoms on mango in various orchards in Perak. Therefore, this research aimed to: 1. Isolate and identify SBFS fungi on mango collected from Perak, Pahang, and Perlis based on morphological and molecular approaches; 2. Assess the phylogenetic relationship among the SBFS fungal isolates; 3. Determine the pathogenicity of the SBFS fungi isolated from mango. A total of 87 mango fruit showing SBFS disease symptoms were collected, and the number of SBFS colonies on each mango (CPM) and the percentage area of SBFS infection were determined. Subsequently, 2106 mango peel samples were obtained and subjected to isolation. Morphological characterization resulted in the identification of 33 pure cultures belonging to SBFS fungal genera, such as Zasmidum, Peltaster, Exophiala, Pseudocercospora, and Ochroconis. The DNA sequencing of the internal transcribed spacer (ITS) and large subunit (LSU) confirmed 18 representative isolates as distinct species, including Z. citrigriseum, Z. aporosae, Peltaster-like species, ‘Pseudopeltaster’, E. bergeri, E. spinifera, Pseudocercospora species, and O. cordanae. Phylogenetic analyses using maximum parsimony (MP) and maximum likelihood (ML) approaches indicated that the SBFS fungal complex on mango was related to both known SBFS members globally and non-SBFS taxa.
Unveiling Limestone Orchid Hotspots In The Karst Hills Of Northern Peninsular Malaysia
(2024-09)
Bakar, Shahrul Nizam Abu
A significant knowledge gap remains regarding the diversity of orchids in the limestone hills of northern Peninsular Malaysia, especially in Kedah and Perak. Addressing this knowledge gap requires thorough comprehensive assessments and proper documentations of orchid diversity and endemism in this unique karst habitat. To fulfill this, 10 field assessments have been carried out between Mac 2021 to November 2022 to five selected limestone hills in Kedah and Perak state boundary, aimed to assess the diversity of limestone orchids and their species richness, evaluating the threats facing by the orchids and their natural habitat, determining areas with high diversity hotspots, and proposing new conservation status for the rare and endangered orchid species with restricted distribution and small population size. A total of 134 orchid species represented in 68 genera have been recorded from Gunung Batu Putih, Gunung Pong, Gunung Baling, Gunung Pulai and Gunung Fakir Terbang. From the five limestone hills, Gunung Batu Putih was known to have the most richest and diverse orchid species with a total of 105 species from 58 genera (H’ = 4.504 and D = 0.9875), followed by Gunung Pong with 103 species from 57 genera (H’ = 4.471 and D = 0.9867), Gunung Baling with 93 species from 50 genera (H’ = 4.366 and D = 0.9853), Gunung Pulai with 90 species from 49 genera (H’ = 4.296 and D = 0.9838) and lastly Gunung Fakir Terbang with 67 species from 29 genera (H’ = 3.88 and D = 0.9756). From the account, 36 species are recognized as new records to Kedah and three species as new records to Peninsular Malaysia, namely Anoectochilus sanguineus P.T.Ong & P.O’Byrne, Bulbophyllum meson J.J.Verm., Schuit. & de Vogel and Luisia brachystachys (Lindl.) Blume. Three species endemic to Peninsular Malaysia were gathered in this study which are Anoectochilus sanguineus, Cheirostylis goldschmidtiana Schltr. and Phalaenopsis appendiculata Carr. This study has also revealed the relationships between the diversity of orchids and the influences of certain environmental factors. Only soil pH and relative humidity (RH) were found to be positively correlated with orchid’s species richness. The analysis on species distribution data has shown that Gunung Batu Putih to have the highest number of hotspot areas followed by Gunung Pong, Gunung Baling, Gunung Pulai and Gunung Fakir Terbang. New conservation status have been proposed to the selected rare and endangered orchids, which four species were proposed as Critically Endangered (CR) (Aerides krabiensis, Anoectochilus albolineatus, Goodyera hispida and Phalaenopsis appendiculata), and four as Endangered (EN) (Anoectochilus sanguineus, Cheirostylis goldschmidtiana, Paphiopedilum niveum and Spathoglottis hardingiana).
Compatibility And Biodegradability Of Biopolyester-Based Blends With Poly(3-Hydroxybutyrate-Co-3-Hydroxyhexanoate) (Phbh) As A Blend Matrix
(2024-07)
Jeepery, Iffa Farahin
Poly(3-hydroxybutyrate-co-3-hydroxyhexanoate) (phbh) has been evaluated to have excellent degradability in marine environment. However, its performance for application is still limited. A series of properties enhancement is deemed necessary to improve the potential of phbh being both a high-performance material and readily biodegradable. In this study, phbh containing 5 and 17 mol% 3-hydroxyhexanoate (3hh) were blended with atactic poly(3-hydroxybutyrate) (phb), polycaprolactone (pcl), and polybutylene succinate (pbs) at different ratios by the solvent-casting method. Phbh-5%/atactic phb and phbh-17%/atactic phb showed a single glass-transition temperature (tg), indicating miscibility in the amorphous state. Immiscibility was observed in the phbh-5%/pcl and phbh-17%/pcl blends based on the non-transitioning tg of the phbh component, presence of two distinct tg values for some of the blend films, and individual crystallization manner. The thermal properties and spherulitic morphologies of the phbh-5%/pbs blend films suggested partial miscibility. The enzymatic degradability of the three types of blends by ralstonia pickettii t1 phb depolymerase and burkholderia cepacia lipase was investigated. Depending on the enzyme–substrate specificity, miscibility, and phase structure of the blend, the enzymatic erosion rate was different among the three types of blends.
Polyhydroxyalkanoates Production By Cupriavidus Necator Transformants Harboring Polyhydroxyalkanoate Synthase Of Chromobacterium Sp. Usm2 (Phaccs) And Its Potential Application For Lipase Assay Kit
(2024-05)
Tang, Hui Jia
Polyhydroxyalkanoates (phas) are biopolyesters produced by microorganisms as carbon storage in the presence of abundant carbon sources and the limitation of growth nutrients. Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) [p(3hb-co-4hb)] has been used for industrial applications, including packaging, biodegradable plastics, medical devices, and biomedical applications, owing to its biodegradability properties. Chromobacterium sp. Usm2 was isolated in langkawi, malaysia, and was able to accumulate pha. Pha synthase of chromobacterium sp. Usm2 (phaccs) was able to polymerize various monomers such as 3-hydroxybutyrate (3hb), 3-hydroxyvalerate (3hv), and 3-hydroxyhexanoate (3hhx) from carbon sources or precursors due to its broad substrate specificity. To date, there is no report on the potential of phaccs to produce p(3hb-co-4hb) copolymer. In this study, a series of optimization tests and pha biosynthesis were performed to investigate the potential of the heterologous expression of phaccs in c. Necator transformants to produce p(3hb-co-4hb) using 4hb-structurally related precursors such as 1,6-hexanediol, 1,4-butanediol, γ-butyrolactone, and sodium 4-hydroxybutyrate. The polymers obtained were then further characterized to determine their monomer compositions, thermal properties, and lipase depolymerizing activity.

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