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Lightning is a naturally occurring phenomenon that involves a sudden electrostatic discharge caused by an imbalance between electrically charged cloud regions. Although lightning is visibly amazing, its impact can be dangerous and damaging, which many studies have carried out lightning-generated electric field measurements to assess the electrical discharge features. This study conducted the lightning-generated electric field measurement on the College of Engineering building rooftop at UNITEN from August 2019 to March 2020. A total of 115 negative lightning return strokes waveforms were recorded using a parallel plate antenna. A comparison was made between the data measured in the tropical and non-tropical regions, such as UTM, UPM, Sweden, USA, and Germany, in terms of the characteristic, mainly on the negative return strokes parameters. It was observed that data measured in the same region, either tropical or non-tropical, were consistent or almost similar. On the contrary, the results indicated a significant difference between these two regions on the negative return strokes parameters characteristics. The zero-to-peak and fast transition 10–90% rise time, as well as width dE/dt pulse at half peak value in the tropical region, were observed higher than the non-tropical region. Meanwhile, the zero-crossing time and slow front amplitude relative to the peak in the non-tropical region were averagely longer as compared to the tropical region. Therefore, dissimilarities in the characteristics of negative return stroke parameters could be attributed to the variation in the meteorological conditions, geographical locations, and climatic affection.

In modern urban society, plastic has become a major component in many applications. Despite their usefulness, plastics are known for their alarming resistance to biodegradation and therefore pose a huge burden on the environment. The surge in plastic waste has led to the development of biodegradable plastics. Biodegradable plastics are perceived to be one of the sustainable ways to reduce plastic wastes. Among the biodegradable plastics, polylactic acid (PLA), a bio-based plastic, has been widely used for diverse applications. PLA however, is known to be less susceptible to biodegradation and requires longer time to degrade in the natural environment compared to other aliphatic polyesters. Therefore, identification of PLA-degraders is the current focus of research. Potential PLA-degraders have been isolated from various sources, but the number is still limited. Considering temperature as one of the important factors in biodegradation, in this review, we categorize PLA degraders into three groups; thermophilic, mesophilic and psychrophilic, and discuss their relevance to PLA biodegradation. Enzymes associated with PLA degradation are described according to their temperature preference. One of the current limitations is the structural insights into the catalytic mechanism. Discovery of more PLA-degraders and understanding of the mechanism could aid in designing strategies to accelerate the biodegradation process.

Candidiasis is a fungal infection caused by Candida spp. especially Candida albicans, C. glabrata, C. parapsilosis and C. tropicalis. Although the medicinal therapeutic strategies have rapidly improved, the mortality rate as candidiasis has continuously increased. The secreted and membrane-bound virulence factors (VFs) are responsible for fungal invasion, damage and translocation through the host enterocytes besides the evasion from host immune system. VFs such as agglutinin-like sequences (Als), heat shock protein 70, phospholipases, secreted aspartyl proteinases (Sap), lipases, enolases and phytases are mostly hydrolases which degrade or interact with the enterocyte membrane components. Candidalysin, however, acts as a peptide toxin to induce necrotic cell lysis. To date, structural studies of the VFs remain underexplored, hindering their functional analyses. Among the VFs, only Sap and Als have their structures deposited in Protein Data Bank (PDB). Therefore, this review scrutinizes the mechanisms of these VFs by discussing the VF-deficient studies of several Candida spp. and their abilities to produce these VFs. Nonetheless, their latest reported sequential and structural analyses are discussed to impart a wider perception of the host-pathogen interactions and potential vaccine or antifungal drug targets. This review signifies that more VFs structural investigations and mining in the emerging Candida spp. are required to decipher their pathogenicity and virulence mechanisms compared to the prominent C. albicans.

Aminopeptidase P (APPro, E.C 3.4.11.9) cleaves N-terminal amino acids from peptides and proteins where the penultimate residue is proline. This metal-ion-dependent enzyme shares a similar fold, catalytic mechanism, and substrate specificity with methionine aminopeptidase and prolidase. It adopts a canonical pita bread fold that serves as a structural basis for the metal-dependent catalysis and assembles as a tetramer in crystals. Similar to other metalloaminopeptidase, APPro requires metal ions for its maximal enzymatic activity, with manganese being the most preferred cation. Microbial aminopeptidase possesses unique characteristics compared with aminopeptidase from other sources, making it a great industrial enzyme for various applications. This review provides a summary of recent progress in the study of the structure and function of aminopeptidase P and describes its various applications in different industries as well as its significance in the environment.

Microbial lipases represent one of the most important groups of biotechnological biocatalysts. However, the high-level production of lipases requires an understanding of the molecular mechanisms of gene expression, folding, and secretion processes. Stable, selective, and productive lipase is essential for modern chemical industries, as most lipases cannot work in different process conditions. However, the screening and isolation of a new lipase with desired and specific properties would be time consuming, and costly, so researchers typically modify an available lipase with a certain potential for minimizing cost. Improving enzyme properties is associated with altering the enzymatic structure by changing one or several amino acids in the protein sequence. This review detailed the main sources, classification, structural properties, and mutagenic approaches, such as rational design (site direct mutagenesis, iterative saturation mutagenesis) and direct evolution (error prone PCR, DNA shuffling), for achieving modification goals. Here, both techniques were reviewed, with different results for lipase engineering, with a particular focus on improving or changing lipase specificity. Changing the amino acid sequences of the binding pocket or lid region of the lipase led to remarkable enzyme substrate specificity and enantioselectivity improvement. Site-directed mutagenesis is one of the appropriate methods to alter the enzyme sequence, as compared to random mutagenesis, such as error-prone PCR. This contribution has summarized and evaluated several experimental studies on modifying the substrate specificity of lipases.

Citrobacter sp. S-77 [NiFe]-hydrogenase harbors a standard [4Fe–4S] cluster proximal to the Ni–Fe active site. The presence of relocatable water molecules and a flexible aspartate enables the [4Fe–4S] to display redox-dependent conformational changes. These structural features are proposed to be the key aspects that protect the active site from O2 attack.

Structural comparison of wild-type F1 protease and thermophilic homologues leads to hypothesis about the role of ion pairs for the thermostability of the enzymes. Higher thermostability was found to correlate with an increased number of the residues involved in ion pairs or ion pair’s networks. Therefore, W200R protease is a mutant designed to have three new additional ion pairs compared to the F1 protease. This designed mutant underwent substitution of Trp (Tryptophan) at position 200 with Arg (Arginine). Both of protease and W200R were cloned into pGEX-4T1 vector and transformed into E. coli BL21 (DE3)pLysS. For the purpose of characterization, F1 protease was purified by using Glutathione Sepharose resin and heat treatment whereby W200R was purified in three steps; Glutathione Sepharose resin, ion exchange by using Q-Sepharose Fast Flow resin and Phenyl Sepharose High Performance. The last product of purification for F1 protease and W200R was confirmed to be the mature form which is approximately 27 kDa. Characterization of W200R’s thermostability was done in comparison with F1 protease. The optimum temperature of W200R protease in the presence and absence of 2 mM CaCl2 was 75°C. Meanwhile, F1 protease exhibited a lower temperature optimum which is 70°C with the presence and absence of Ca2+. In term of thermostability in the presence of 2 mM Ca2+, the activity of W200R and F1 protease retained 100% of its activity between 50°C to 80°C and 50°C to 65°C, respectively. Ca2+ affected both enzymes by increasing and stabilizing the protease activity. The optimum pH of W200R was at pH 8 and the activity was stable in pH ranging from pH 7.0-10. The activity of W200R retained more than 100% of its activity compared to the control in the presence of miscible organic solvents log P < 2 such as pyridine, ethanol, methanol and DMSO. In comparison with the wild type, stability in the presence of immiscible organic solvents log P > 2 such as n- heptanes, hexane and benzene was