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Fulltext Small scale imaging using ultrasonic tomography

Zakaria, Z., Fazalul Rahiman, M.H., Abdul Rahim, R., Megat Ali, M.S.A., Baharuddin, M.Y., Jahidin, A.H.

Journal of Nuclear and Related Technologies, 2009;2009(1):266-281.
MyJurnal

Ultrasound technology progressed through the 1960’s from simple A-mode and B-mode scans to today’s M-mode and Doppler two dimensional (2-D) and even three dimensional (3-D) systems. Modern ultrasound imaging has its roots in sonar technology after it was first described by Lord John Rayleigh over 100 years ago on the interaction of acoustic waves with media. Tomography technique was developed as a diagnostic tool in the medical area since the early of 1970’s. This research initially focused on how to retrieve a cross sectional images from living or non-living things. After a decade, the application of tomography systems span into the industrial area. However, the long exposure time of medical radiation-based method cannot tolerate the dynamic changes in industrial process two phase liquid/gas flow system.. An alternative system such as a process tomography system, can give information on the nature of the flow regime characteristic. The overall aim of this paper is to investigate the use of a small scale ultrasonic tomography method based on ultrasonic transmission mode tomography for online monitoring of liquid/gas flow in pipe/vessel system through ultrasonic transceivers application. This non-invasive technique applied sixteen transceivers as the sensing elements to cover the pipe/vessel cross section. The paper also details the transceivers selection criteria, hardware setup, the electronic measurement circuit and also the image reconstruction algorithm applied. The system was found capable of visualizing the internal characteristics and provides the concentration profile for the corresponding liquid and gas phases.
Fulltext Optical tomography: real time image reconstruction for various flow regimes in gravity flow conveyor

Abdul Rahim, R., Pang, J.F., Chan, K.S., Leong, L.C., Fazalul Rahiman, M.H.

ASM Science Journal, 2007;1(1):27-36.
MyJurnal

In this study, real-time imaging was monitored for flowing solid particles when various baffles were created to block certain areas of the pipe. The generated flow regimes were full-flow, three-quarter-flow, half-flow and quarter-flow. A vertical pneumatic conveyor was designed to hold a 85 mm inner diameter pipeline. The four projection optical tomography systems used, applied the parallel beam projection approach and use infrared light sources so that the sensor was free of noise from the surrounding visible light source. The two orthogonal and two rectilinear projections were axial, but ideally they should have been in the same layer. The sensor readings could be related to the varying light intensity effects of the dropping particles and were used to provide cross-sectional distribution information for the conveyor. By using computer programming, the information was reconstructed to produce coloured images and concentration was obtained by reference to a colour code. The results obtained from this study showed how imaged flow followed the artificial flow regime. This study could benefit industrial production lines in maintaining the desired flow rates.
Fulltext The effect of flaxseed extract on skin elasticity of the healing wound in rabbits.

Abdul Jabbar O, Kashmoola MA, Mustafa Al-Ahmad BE, Mokhtar KI, Muhammad N, Abdul Rahim R, et al.

IIUM Medical Journal Malaysia, 2019;18(1):5-12.
MyJurnal

Management of disturbed wounds, large skin defects and the areas where skin tension precludes wound closure is of high clinical importance. Healing in wounds occurs through epithelization and contraction processes (second-intentions healing) that may result in certain undesirable complications including keloid and formation of a fragile epithelial layer.Materials and methods: 27 white New Zealand rabbit included in this study divided into 3 groups; one group of 9 rabbits received Flaxseed gel topically for three time intervals (1, 7, and 14 days); a second group received Fucidin cream as positive control, while a third group has not received any treatment as negative control, Skin elasticity measurements were performed using the DermaLab system. Results: Throughout the study, skin elasticity was significantly greater in Flaxseed group than in others. Flaxseed decrease elasticity value from (3.46 ± 2.05). Hence, Young's modulus of skin elasticity in flaxseed group was (2.46 ± 1.02) after 14 days (p = 0.003), while no significant differences were evident in both Fucidin group (1.16 ± 0.77) and non-treated group (1.86 ± 1.40) (p = 0.019), accordingly flaxseed extract more reproducible than other groups demonstrating comparable efficacy in skin elasticity and distensibility.Conclusions: This study showed the therapeutic effect of flaxseed on biologic tissue. Elasticity evaluation demonstrated increased density and firmness in the network of collagen fibers in the dermis and subcutis during wound healing process promise in generating therapeutic gel to be used in wound healing process.
Fulltext Neural network and principal component regression in non-destructive soluble solids content assessment: a comparison

Chia KS, Abdul Rahim H, Abdul Rahim R

J Zhejiang Univ Sci B, 2012 Feb;13(2):145-51.
PMID: 22302428 DOI: 10.1631/jzus.B11c0150

Visible and near infrared spectroscopy is a non-destructive, green, and rapid technology that can be utilized to estimate the components of interest without conditioning it, as compared with classical analytical methods. The objective of this paper is to compare the performance of artificial neural network (ANN) (a nonlinear model) and principal component regression (PCR) (a linear model) based on visible and shortwave near infrared (VIS-SWNIR) (400-1000 nm) spectra in the non-destructive soluble solids content measurement of an apple. First, we used multiplicative scattering correction to pre-process the spectral data. Second, PCR was applied to estimate the optimal number of input variables. Third, the input variables with an optimal amount were used as the inputs of both multiple linear regression and ANN models. The initial weights and the number of hidden neurons were adjusted to optimize the performance of ANN. Findings suggest that the predictive performance of ANN with two hidden neurons outperforms that of PCR.
Fulltext Molecular characterization of a recombinant manganese superoxide dismutase from Lactococcus lactis M4

Tan BH, Chor Leow T, Foo HL, Abdul Rahim R

Biomed Res Int, 2014;2014:469298.
PMID: 24592392 DOI: 10.1155/2014/469298

A superoxide dismutase (SOD) gene of Lactococcus lactis M4 was cloned and expressed in a prokaryotic system. Sequence analysis revealed an open reading frame of 621 bp which codes for 206 amino acid residues. Expression of sodA under T7 promoter exhibited a specific activity of 4967 U/mg when induced with 1 mM of isopropyl-β-D-thiogalactopyranoside. The recombinant SOD was purified to homogeneity by immobilised metal affinity chromatography and Superose 12 gel filtration chromatography. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and western blot analyses of the recombinant SOD detected a molecular mass of approximately 27 kDa. However, the SOD was in dimer form as revealed by gel filtration chromatography. The purified recombinant enzyme had a pI of 4.5 and exhibited maximal activity at 25°C and pH 7.2. It was stable up to 45°C. The insensitivity of this lactococcal SOD to cyanide and hydrogen peroxide established that it was a MnSOD. Although it has 98% homology to SOD of L. lactis IL1403, this is the first elucidated structure of lactococcal SOD revealing active sites containing the catalytic manganese coordinated by four ligands (H-27, H-82, D-168, and H-172).
Fulltext Purification and Characterization of a Thermostable Lipase from Geobacillus thermodenitrificans IBRL-nra

Balan A, Ibrahim D, Abdul Rahim R, Ahmad Rashid FA

Enzyme Res, 2012;2012:987523.
PMID: 23198138 DOI: 10.1155/2012/987523

Thermostable lipase from Geobacillus thermodenitrificans IBRL-nra was purified and characterized. The production of thermostable lipase from Geobacillus thermodenitrificans IBRL-nra was carried out in a shake-flask system at 65°C in cultivation medium containing; glucose 1.0% (w/v); yeast extract 1.25% (w/v); NaCl 0.45% (w/v) olive oil 0.1% (v/v) with agitation of 200 rpm for 24 hours. The extracted extracellular crude thermostable lipase was purified to homogeneity by using ultrafiltration, Heparin-affinity chromatography, and Sephadex G-100 gel-filtration chromatography by 34 times with a final yield of 9%. The molecular weight of the purified enzyme was estimated to be 30 kDa after SDS-PAGE analysis. The optimal temperature for thermostable lipase was 65°C and it retained its initial activity for 3 hours. Thermostable lipase activity was highest at pH 7.0 and stable for 16 hours at this pH at 65°C. Thermostable lipase showed elevated activity when pretreated with BaCl(2), CaCl(2), and KCl with 112%, 108%, and 106%, respectively. Lipase hydrolyzed tripalmitin (C16) and olive oil with optimal activity (100%) compared to other substrates.
Lensed optical fiber sensors for on-line measurement of flow

Ibrahim S, Green RG, Dutton K, Abdul Rahim R

ISA Trans, 2002 Jan;41(1):13-8.
PMID: 12014798

This paper describes a system using lensed optical fiber sensors that are arranged in the form of two orthogonal projections. The sensors are placed around a process vessel for upstream and downstream measurements. The purpose of the system is for on-line monitoring of particles and droplets being conveyed by a fluid. The lenses were constructed using a custom heating fixture. The fixture enables the lenses to be constructed with similar radii resulting in identical characteristics with minimum differences in transmitted intensity and emission angle. By collimating radiation from two halogen bulbs, radiation can be obtained by the sensors with radiation intensity related to the nature of the media. Each sensor interrogates a finite section of the measurement section. Each sensor provides a view. Parallel sensors provide a projection. Signal processing is carried out on the measured data in the time and frequency domains to investigate the latent information present in the flow signals.
Fulltext Effects of lysine and methionine in a low crude protein diet on the growth performance and gene expression of immunity genes in broilers

Lee CY, Song AA, Loh TC, Abdul Rahim R

Poult Sci, 2020 Jun;99(6):2916-2925.
PMID: 32475425 DOI: 10.1016/j.psj.2020.03.013

Globally, the poultry industry is 1 of the most advanced livestock industries. Feed contributes to the biggest proportion (65-70%) of the production cost. Most feed ingredients in Malaysia are imported, which contributes to the high food bill annually, and alternative feed formulation may help decrease the cost of poultry feed. Feed formulation are improved to efficiently meet the dietary requirements of the broilers and 1 of the ways is by reducing the level of crude protein in the diet while supplementing essential amino acids. In this study, the effects of methionine and lysine, which are the 2 most limiting amino acids in the chicken diet, were supplemented in a low crude protein diet, and its effects on the growth and expression of immunity genes such as MUC2, SLC, GAL6, and LEAP-2 were studied. A total of 300 Cobb500 broilers were tested with 10 different dietary treatments. Experimental treatment diets consist of high, standard, and low levels of methionine and lysine in the diet with reduced crude protein. The control group consists of diet with standard levels of lysine, methionine, and crude protein as recommended for Cobb500 broilers. Ribonucleic acid was extracted from the jejunum, spleen, and liver for gene expression analysis which was performed with real-time polymerase chain reaction using SYBR Green chemistry. Results of the growth performance at 6 wk showed improved feed conversion ratio when lysine was increased by 0.2% in a low crude protein diet at 1.96 ± 0.11. Gene expression of MUC2 gene in the jejunum showed a significant increase across all experimental diets with the treatment with higher lysine in low crude protein diet with the highest increase of 3.8 times as compared with the control diet. The other genes expressed in the spleen and liver were mostly downregulated. It was concluded that supplementation of high lysine with standard methionine in a low crude protein diet performed better in terms of lowest feed conversion ratio and high upregulation of MUC2 gene.
Global Transcriptome Analysis of Gracilaria changii (Rhodophyta) in Response to Agarolytic Enzyme and Bacterium

Lim EL, Siow RS, Abdul Rahim R, Ho CL

Mar Biotechnol (NY), 2016 Apr;18(2):189-200.
PMID: 26631182 DOI: 10.1007/s10126-015-9680-6

Many bacterial epiphytes of agar-producing seaweeds secrete agarase that degrade algal cell wall matrix into oligoagars which elicit defense-related responses in the hosts. The molecular defense responses of red seaweeds are largely unknown. In this study, we surveyed the defense-related transcripts of an agarophyte, Gracilaria changii, treated with β-agarase through next generation sequencing (NGS). We also compared the defense responses of seaweed elicited by agarase with those elicited by an agarolytic bacterium isolated from seaweed, by profiling the expression of defense-related genes using quantitative reverse transcription real-time PCR (qRT-PCR). NGS detected a total of 391 differentially expressed genes (DEGs) with a higher abundance (>2-fold change with a p value <0.001) in the agarase-treated transcriptome compared to that of the non-treated G. changii. Among these DEGs were genes related to signaling, bromoperoxidation, heme peroxidation, production of aromatic amino acids, chorismate, and jasmonic acid. On the other hand, the genes encoding a superoxide-generating NADPH oxidase and related to photosynthesis were downregulated. The expression of these DEGs was further corroborated by qRT-PCR results which showed more than 90 % accuracy. A comprehensive analysis of their gene expression profiles between 1 and 24 h post treatments (hpt) revealed that most of the genes analyzed were consistently upregulated or downregulated by both agarase and agarolytic bacterial treatments, indicating that the defense responses induced by both treatments are highly similar except for genes encoding vanadium bromoperoxidase and animal heme peroxidase. Our study has provided the first glimpse of the molecular defense responses of G. changii to agarase and agarolytic bacterial treatments.
Determination and Quantification of the Vinblastine Content in Purple, Red, and White Catharanthus Roseus Leaves Using RP-HPLC Method

Abdul Rahim R, Ahmad NH, Al Azzam KM, Mat I

Adv Pharm Bull, 2018 Mar;8(1):157-161.
PMID: 29670851 DOI: 10.15171/apb.2018.019

Purpose:
To determine and quantify vinblastine in different varieties of Catharanthus roseus using reversed-phase HPLC method.
Methods:
The liquid chromatographic separation was performed using a reversed phase C18, Microsorb - MV column (250 mm x 4.6 mm, 5 µm) at room temperature and eluted with a mobile phase containing methanol - phosphate buffer (5 mM, pH 6.0) - acetonitrile with different proportion gradient elution at a flow rate of 2.0 mL min-1 and detection at 254 nm.
Results:
The HPLC method was utilized for the quantification of vinblastine in purple, red and white varieties of Catharanthus roseus leaves. The separation was achieved in less than 8 min. The peak confirmation was done based on the retention times and UV spectra of the reference substance. The method was validated with respect to linearity, precision, recovery, limit of detection and quantification. Results showed that the purple variety gives 1.2 and 1.5 times more vinblastine concentration compared to the white and pink varieties, respectively.
Conclusion:
The obtained results from different varieties are thus useful for the purpose of vinblastine production from Catharanthus roseus plant.
Hydrogel beads bio-nanocomposite based on Kappa-Carrageenan and green synthesized silver nanoparticles for biomedical applications

Azizi S, Mohamad R, Abdul Rahim R, Mohammadinejad R, Bin Ariff A

Int J Biol Macromol, 2017 Nov;104(Pt A):423-431.
PMID: 28591593 DOI: 10.1016/j.ijbiomac.2017.06.010

This paper describes the fabrication and characterization of bio-nanocomposite hydrogel beads based on Kappa-Carrageenan (κ-Carrageenan) and bio-synthesized silver nanoparticles (Ag-NPs). The silver nanoparticles were prepared in aqueous Citrullus colocynthis seed extract as both reducing and capping agent. Cross-linked κ-Carrageenan/Ag-NPs hydrogel beads were prepared using potassium chloride as the cross-linker. The hydrogel beads were characterized using XRD and FESEM. Moreover, swelling property of the hydrogel beads was investigated. The Ag release profile of the hydrogels was obtained by fitting the experimental data to power law equation. The direct visualization of the green synthesized Ag-NPs using TEM shows particle size in the range of 23±2nm. The bio-nanocomposite hydrogels showed lesser swelling behavior in comparison with pure κ-Carrageenan hydrogel. Regardless the slow Ag release, κ-Carrageenan/Ag-NPs presented good antibacterial activities against Staphylococcus aureus, Methicilin Resistant Staphylococcus aurous, Peseudomonas aeruginosa and Escherichia coli with maximum zones of inhibition 11±2mm. Cytotoxicity study showed that the bio-nanocomposite hydrogels with non-toxic effect of concentration below 1000μg/mL have great pharmacological potential and a suitable level of safety for use in the biological systems.
Fulltext Engineering integrative vectors based on phage site-specific recombination mechanism for Lactococcus lactis

Koko I, Song AA, Masarudin MJ, Abdul Rahim R

BMC Biotechnol, 2019 11 27;19(1):82.
PMID: 31775775 DOI: 10.1186/s12896-019-0575-x

BACKGROUND: Site-specific integration system allows foreign DNA to be integrated into the specific site of the host genome, enabling stable expression of heterologous protein. In this study, integrative vectors for secretion and surface display of proteins were constructed based on a lactococcal phage TP901-1 integrating system.
RESULTS: The constructed integration system comprises of a lactococcal promoter (PnisA or P170), phage attachment site (attP) from bacteriophage TP901-1, a signal peptide (USP45 or SPK1) for translocation of the target protein, and a PrtP344 anchor domain in the case of the integrative vectors for surface display. There were eight successfully constructed integrative vectors with each having a different combination of promoter and signal peptide; pS1, pS2, pS3 and pS4 for secretion, and pSD1, pSD2, pSD3 and pSD4 for surface display of desired protein. The integration of the vectors into the host genome was assisted by a helper vector harbouring the integrase gene. A nuclease gene was used as a reporter and was successfully integrated into the L. lactis genome and Nuc was secreted or displayed as expected. The signal peptide SPK1 was observed to be superior to USP45-LEISSTCDA fusion in the secretion of Nuc. As for the surface display integrative vector, all systems developed were comparable with the exception of the combination of P170 promoter with USP45 signal peptide which gave very low signals in whole cell ELISA.
CONCLUSION: The engineered synthetic integrative vectors have the potential to be used for secretion or surface display of heterologous protein production in lactococcal expression system for research or industrial purposes, especially in live vaccine delivery.
Fulltext Outcomes of Prostate Artery Embolisation in Patients with Severe Symptoms of Benign Prostate Hyperplasia

Abdul Rahim R, Eng Hong G, Nik Ismail NA, Zakaria R

Malays J Med Sci, 2021 Dec;28(6):55-63.
PMID: 35002490 DOI: 10.21315/mjms2021.28.6.6

Background: Benign prostatic hyperplasia (BPH) is associated with severe lower urinary tract symptoms (LUTS). The severity of LUTS is assessed by the International Prostate Symptoms Score (IPSS). Prostate artery embolisation (PAE) is a newly available method for combating LUTS. This study aims to assess the outcomes of PAE in reducing LUTS and prostate volume in patients with BPH.
Methods: Patients diagnosed with BPH with severe LUTS who had undergone PAE were included. Their IPSS score was ≥ 20 despite medical therapy. PAE was performed via the unilateral femoral artery using various types of embolic material. Bilateral or unilateral embolisation of the prostate artery was considered a technical success. The severity of LUTS pre- and post-PAE were assessed using IPSS while prostate volume pre- and post-PAE were assessed by ultrasound and magnetic resonance imaging (MRI).
Results: Ninety percent of patients had technical success and one required transurethral resection of the prostate (TURP). The mean IPSS reduction at the final follow-up was 12.9 (P < 0.028). The mean reduction of prostate volume at the last follow-up by ultrasound was 114.99 mL (P < 0.028) and by MRI was 29.17 mL (P < 0.028).
Conclusion: PAE is safe and effective in reducing severe LUTS and prostate gland volume in BPH patients.
Real time mass flow rate measurement using multiple fan beam optical tomography

Abdul Rahim R, Leong LC, Chan KS, Rahiman MH, Pang JF

ISA Trans, 2008 Jan;47(1):3-14.
PMID: 17709106

This paper presents the implementing multiple fan beam projection technique using optical fibre sensors for a tomography system. From the dynamic experiment of solid/gas flow using plastic beads in a gravity flow rig, the designed optical fibre sensors are reliable in measuring the mass flow rate below 40% of flow. Another important matter that has been discussed is the image processing rate or IPR. Generally, the applied image reconstruction algorithms, the construction of the sensor and also the designed software are considered to be reliable and suitable to perform real-time image reconstruction and mass flow rate measurements.
Infrared tomography: data distribution system and software development for real-time velocity measurement

Abdul Rahim R, Pang JF, Chan KS, Leong LC, Sulaiman S, Abdul Manaf MS

ISA Trans, 2007 Apr;46(2):131-45.
PMID: 17367791

The data distribution system of this project is divided into two types, which are a Two-PC Image Reconstruction System and a Two-PC Velocity Measurement System. Each data distribution system is investigated to see whether the results' refreshing rate of the corresponding measurement can be greater than the rate obtained by using a single computer in the same measurement system for each application. Each system has its own flow control protocol for controlling how data is distributed within the system in order to speed up the data processing time. This can be done if two PCs work in parallel. The challenge of this project is to define the data flow process and critical timing during data packaging, transferring and extracting in between PCs. If a single computer is used as a data processing unit, a longer time is needed to produce a measurement result. This insufficient real-time result will cause problems in a feedback control process when applying the system in industrial plants. To increase the refreshing rate of the measurement result, an investigation on a data distribution system is performed to replace the existing data processing unit.
Fulltext Molecular characterisation of new organisation of plnEF and plw loci of bacteriocin genes harbour concomitantly in Lactobacillus plantarum I-UL4

Tai HF, Foo HL, Abdul Rahim R, Loh TC, Abdullah MP, Yoshinobu K

Microb Cell Fact, 2015;14:89.
PMID: 26077560 DOI: 10.1186/s12934-015-0280-y

Bacteriocin-producing Lactic acid bacteria (LAB) have vast applications in human and animal health, as well as in food industry. The structural, immunity, regulatory, export and modification genes are required for effective bacteriocin biosynthesis. Variations in gene sequence, composition and organisation will affect the antimicrobial spectrum of bacteriocin greatly. Lactobacillus plantarum I-UL4 is a novel multiple bacteriocin producer that harbours both plw and plnEF structural genes simultaneous which has not been reported elsewhere. Therefore, molecular characterisation of bacteriocin genes that harboured in L. plantarum I-UL4 was conducted in this study.
Molecular characterization of Vibrio cholerae O1 outbreak strains in Miri, Sarawak (Malaysia)

Radu S, Vincent M, Apun K, Abdul-Rahim R, Benjamin PG, Yuherman, et al.

Acta Trop, 2002 Aug;83(2):169-76.
PMID: 12088858

Bacterial resistance to various antimicrobial agents is common in area with high usage of antibiotics. In this study, the data on antimicrobial susceptibility patterns of Vibrio cholerae O1 from patients during an outbreak period was found to be high but variable rates of multidrug resistance. Thirty-two of 33 V. cholerae isolates harboured the tcp, ctx, zot and ace genes, suggesting their possible roles in the outbreak cases. We analyzed the molecular diversity of a total of 33 strains of V. cholerae O1 isolated from 33 patients between November 1997 and April 1998 using random amplified polymorphic DNA (RAPD) analysis. The 30 typable isolates could be separated into four major clusters containing 5, 17, 2 and 6 isolates, respectively. However, no particular RAPD pattern was predictive of a particular pattern of antibiotic susceptibility. The findings of this study showed that multiple clones seemed to be responsible for cases in the outbreaks in the study area.
Fulltext Enhancement of Versatile Extracellular Cellulolytic and Hemicellulolytic Enzyme Productions by Lactobacillus plantarum RI 11 Isolated from Malaysian Food Using Renewable Natural Polymers

Mohamad Zabidi NA, Foo HL, Loh TC, Mohamad R, Abdul Rahim R

Molecules, 2020 Jun 03;25(11).
PMID: 32503356 DOI: 10.3390/molecules25112607

Lactobacillus plantarum RI 11 was reported recently to be a potential lignocellulosic biomass degrader since it has the capability of producing versatile extracellular cellulolytic and hemicellulolytic enzymes. Thus, this study was conducted to evaluate further the effects of various renewable natural polymers on the growth and production of extracellular cellulolytic and hemicellulolytic enzymes by this novel isolate. Basal medium supplemented with molasses and yeast extract produced the highest cell biomass (log 10.51 CFU/mL) and extracellular endoglucanase (11.70 µg/min/mg), exoglucanase (9.99 µg/min/mg), β-glucosidase (10.43 nmol/min/mg), and mannanase (8.03 µg/min/mg), respectively. Subsequently, a statistical optimization approach was employed for the enhancement of cell biomass, and cellulolytic and hemicellulolytic enzyme productions. Basal medium that supplemented with glucose, molasses and soybean pulp (F5 medium) or with rice straw, yeast extract and soybean pulp (F6 medium) produced the highest cell population of log 11.76 CFU/mL, respectively. However, formulated F12 medium supplemented with glucose, molasses and palm kernel cake enhanced extracellular endoglucanase (4 folds), exoglucanase (2.6 folds) and mannanase (2.6 folds) specific activities significantly, indicating that the F12 medium could induce the highest production of extracellular cellulolytic and hemicellulolytic enzymes concomitantly. In conclusion, L. plantarum RI 11 is a promising and versatile bio-transformation agent for lignocellulolytic biomass.
Enhanced secretion of cyclodextrin glucanotransferase (CGTase) by Lactococcus lactis using heterologous signal peptides and optimization of cultivation conditions

Mahmud H, Ismail A, Abdul Rahim R, Low KO, Md Illias R

J Biotechnol, 2019 Apr 20;296:22-31.
PMID: 30878516 DOI: 10.1016/j.jbiotec.2019.02.013

In previous studies of Lactococcus lactis, the levels of proteins secreted using heterologous signal peptides were observed to be lower than those obtained using the signal peptide from Usp45, the major secreted lactococcal protein. In this study, G1 (the native signal peptide of CGTase) and the signal peptide M5 (mutant of the G1 signal peptide) were introduced into L. lactis to investigate the effect of signal peptides on lactococcal protein secretion to improve secretion efficiency. The effectiveness of these signal peptides were compared to the Usp45 signal peptide. The highest secretion levels were obtained using the G1 signal peptide. Sequence analysis of signal peptide amino acids revealed that a basic N-terminal signal peptide is not absolutely required for efficient protein export in L. lactis. Moreover, the introduction of a helix-breaking residue in the H-region of the M5 signal peptide caused a reduction in the signal peptide hydrophobicity and decreased protein secretion. In addition, the optimization of cultivation conditions for recombinant G1-CGTase production via response surface methodology (RSM) showed that CGTase activity increased approximately 2.92-fold from 5.01 to 16.89 U/ml compared to the unoptimized conditions.
Secretion of recombinant xylanase in Lactococcus lactis using signal peptides Usp45 and Spk1

Roslan AM, Mustafa Kamil A, Chandran C, Song AA, Yusoff K, Abdul Rahim R

Biotechnol Lett, 2020 Sep;42(9):1727-1733.
PMID: 32335791 DOI: 10.1007/s10529-020-02894-1

OBJECTIVE: The effect of two signal peptides, namely Usp45 and Spk1 on the secretion of xylanase in Lactococcus lactis was analysed.
RESULTS: Xylanase was successfully expressed in Lactococcus lactis. Recombinant xylanase fused to either signal peptide Usp45 or Spk1 showed halo zone on Remazol Brilliant Blue-Xylan plates. This indicated that the xylanase was successfully secreted from the cell. The culture supernatants of strains secreting the xylanase with help of the Spk1 and Usp45 signal peptides contained 49.7 U/ml and 34.4 U/ml of xylanase activity, respectively.
CONCLUSION: Although Usp45 is the most commonly used signal peptide when secreting heterologous proteins in Lactococcus lactis, this study shows that Spk1 isolated from Pediococcus pentosaceus was superior to Usp45 in regard to xylanase protein secretion.

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