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Fulltext The correlation between cytopenia and esophageal varices in patients with liver cirrhosis

Gue CS, Yap CK, Ng HS

Med J Malaysia, 2004 Dec;59(5):604-8.
PMID: 15889562

This retrospective study analysed the case records of 200 patients in the Department of Gastroenterology, Singapore General Hospital from February 2000 to January 2001 who had liver cirrhosis and underwent gastroscopy for the detection of varices. The aim of this study was to determine any relationship between leucopenia, thrombocytopenia and the occurrence of esophageal varices in a cirrhotic population. Our results showed that the diagnostic yield of varices grade 2 and 3 was 6.3% if platelet count was > 150,000/mm3, 25% if platelet count was 100,000 to 150,000/mm3, 38.9% if platelet count was 50,000-99,000/mm3 and 100% if platelet count was <50,000/mm3. Similarly, the diagnostic yield of varices grade 2 and 3 was 19.4% if total white count was > 4,000/mm3, 66.7% if total white count was 3,000- 4,000/mm3 and 94.8% if total white count was < 3,000/mm5. We conclude that thrombocytopenia and leucopenia can be used to stratify risk for occurrence of esophageal varices in cirrhotic patients and gastroscopy will have a high yield for varices when platelet count is < 150,000/mm3 or total white is < 4,000/mm.
Fulltext Gastrointestinal Cytomegalovirus infection in non-human immunodeficiency virus infected patients

Ng KL, Ho J, Ng HS, Luman W

Med J Malaysia, 2003 Aug;58(3):337-44.
PMID: 14750372

This is a retrospective study of fourteen patients who had proven Cytomegalovirus (CMV) infection of the gastrointestinal tract with no Human Immunodeficiency virus infection. The median age was 60.5 (Range 28 to 81) years. Eight patients were below (Group 1) and six above sixty five years old (Group 2). Areas of gastro-intestinal involvement were: oesophagus (2), stomach (1), colon (10) and multiple sites (1). Seven patients from Group 1 had received immunosuppressive therapy at the time of presentation and one had diabetes mellitus. We found a high prevalence of co-morbidities such as chronic renal failure and diabetes mellitus in Group 2. At median follow up of 13.9 months, there was a mortality rate of 50%. Only four patients were treated with ganciclovir. Our study concludes that the gastrointestinal CMV diseases in young patients were associated with immunosuppression whereas the older patients had chronic renal failure or diabetes.
D1S80 (pMCT118) allele frequencies in a Malay population sample from Malaysia

Koh CL, Lim ME, Ng HS, Sam CK

Int J Legal Med, 1997;110(1):39-40.
PMID: 9081241

The D1S80 allele frequencies in 124 unrelated Malays from the Malaysian population were determined and 51 genotypes and 19 alleles were encountered. The D1S80 frequency distribution met Hardy-Weinberg expectations. The observed heterozygosity was 0.80 and the power of discrimination was 0.96.
Recent development in the production strategies of microbial carotenoids

Foong LC, Loh CWL, Ng HS, Lan JC

World J Microbiol Biotechnol, 2021 Jan 04;37(1):12.
PMID: 33392834 DOI: 10.1007/s11274-020-02967-3

Carotenoids are a diverse group of lipid-soluble pigments that exhibit potent biological activities such as antioxidant, anti-inflammatory, and provitamin A activities. The potent health benefits of carotenoids result in the surge in the market demands for carotenoids, especially natural carotenoids from sustainable sources. Microbial carotenoids have attracted considerable interests for many industrial applications because of the low costs and ease of scaling-up with shorter production time. There is a growing interest in the search of new and sustainable microbial sources and cost-efficient production strategies following the high economical values and vast commercial applications of carotenoids. This article presents a review on the industrial production strategies of microbial carotenoids from microalgae, fungi, and bacteria sources. The industrial significance of the mass production of microbial carotenoids is also discussed. The structure, classification, and biosynthesis pathway of the carotenoids are also presented in this review.
Recent development of unconventional aqueous biphasic system: characteristics, mechanisms and applications

Kee PE, Ng TC, Lan JC, Ng HS

Crit Rev Biotechnol, 2020 Jun;40(4):555-569.
PMID: 32283954 DOI: 10.1080/07388551.2020.1747388

Aqueous biphasic system (ABS) is widely used in the recovery, extraction, purification and separation of proteins, enzymes, nucleic acids and antibodies. The ABS with high water content and low interfacial tension offers a biocompatible environment for the recovery of labile biomolecules. Process integration can be achieved using ABS by incorporating multiple-steps of purification, concentration and purification of biomolecules in a single-step operation which often results in high product recovery yield and purity. Conventional ABS is usually formed by aqueous solutions of two polymers or a polymer and a salt above a critical concentration. The high viscosity of polymer-based ABS causes slow phase separation and hinders the mass transfer of biomolecules, whereas polymer/salt ABS is characterized by high ionic strength resulting in the loss of bioactivity of recovered biomolecules. These limitations have encouraged the development of novel ABS which is more cost-effective for various biotechnological applications. This review discusses the characteristics and mechanisms of several types of emerging unconventional ABS using phase-forming components such as hyperbranched polymers, special salts, surfactants, magnetic fields, the addition of nanoparticles and incorporation of various solvent. Moreover, several novel applications of ABS for different separation purposes such as microfluidic-based ABS, ABS bioreactors, application of ABS as an analytical tool, and ABS micropatterning are discussed in this review. In the last section of this review, a comprehensive summary of process integration using ABS for extractive fermentations, bioconversion, crystallization and precipitation is also supplemented for the comprehensive review of various types and applications of ABS in recent years.
Exploring the additive bio-agent impacts upon ectoine production by Halomonas salina DSM5928T using corn steep liquor and soybean hydrolysate as nutrient supplement

Chen PW, Cui ZY, Ng HS, Chi-Wei Lan J

J Biosci Bioeng, 2020 Aug;130(2):195-199.
PMID: 32370929 DOI: 10.1016/j.jbiosc.2020.03.011

Ectoine production using inexpensive and renewable biomass resources has attracted great interest among the researchers due to the low yields of ectoine in current fermentation approaches that complicate the large-scale production of ectoine. In this study, ectoine was produced from corn steep liquor (CSL) and soybean hydrolysate (SH) in replacement to yeast extract as the nitrogen sources for the fermentation process. To enhance the bacterial growth and ectoine production, biotin was added to the Halomonas salina fermentation media. In addition, the effects addition of surfactants such as Tween 80 and saponin on the ectoine production were also investigated. Results showed that both the CSL and SH can be used as the nitrogen source substitutes in the fermentation media. Higher amount of ectoine (1781.9 mg L-1) was produced in shake flask culture with SH-containing media as compared to CSL-containing media. A total of 2537.0 mg L-1 of ectoine was produced at pH 7 when SH-containing media was applied in the 2 L batch fermentation. Moreover, highest amount of ectoine (1802.0 mg L-1) was recorded in the SH-containing shake flask culture with addition of 0.2 μm mL-1 biotin. This study demonstrated the efficacy of industrial waste as the nutrient supplement for the fermentation of ectoine production.
Exploring the fermentation characteristics of a newly isolated marine bacteria strain, Gordonia terrae TWRH01 for carotenoids production

Loh WLC, Huang KC, Ng HS, Lan JC

J Biosci Bioeng, 2020 Aug;130(2):187-194.
PMID: 32334990 DOI: 10.1016/j.jbiosc.2020.03.007

Carotenoids serve as one of the most important group of naturally-occurring lipid-soluble pigments which exhibit great biological activities such as antioxidant, anti-inflammatory and provitamin A activities. Owing to their advantageous health effects, carotenoids are widely applied in various industries. Microbial carotenoids synthesis therefore has attracted increasing attention in recent years. In the present study, a marine microorganism originally isolated from seawater in northern Taiwan was determined to be a strain of Gordonia terrae based on its 16S rRNA gene sequence. The strain G. terrae TWRH01 has the ability to synthesize and accumulate the intracellular pigments was identified by gas chromatography-mass spectrometry (GC-MS). The biochemical production characteristics of this strain were studied by employing different fermentation strategies. Findings suggested that G. terrae TWRH01 can actively grow and efficiently synthesize carotenoids in medium adjusted to pH 7 containing 16 g L-1 sucrose as the carbon source, 16 g L-1 yeast extract as the nitrogen source, 0.6 M NaCl concentration, and supplemented with 0.45% (v/v) 1 M CaCl2. Results revealed that the optimization of fermentation yielded 15.29 g L-1 dry biomass and 10.58 μmol L-1 relative β-carotene concentration. According to GC-MS analysis, the orange-red colored pigments produced were identified as carotenoid derivatives, mainly echinenone and adonixanthin 3'-β-d-glucoside. Therefore, the new bacterial strain showed a highly potential bioresource for the commercial production of natural carotenoids.
Primary purification of intracellular Halomonas salina ectoine using ionic liquids-based aqueous biphasic system

Ng HS, Wan PK, Ng TC, Lan JC

J Biosci Bioeng, 2020 Aug;130(2):200-204.
PMID: 32389469 DOI: 10.1016/j.jbiosc.2020.04.003

Ectoine is a zwitterionic amino acid derivative that can be naturally sourced from halophilic microorganisms. The increasing demands of ectoine in various industries have urged the researches on the cost-effective approaches on production of ectoine. Ionic liquids-based aqueous biphasic system (ILABS) was applied to recover Halomonas salina ectoine from cells hydrolysate. The 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim)BF4 was used in the ILABS and the recovery efficiency of ILABS to recover ectoine from H. salina cells lysate was evaluated by determining the effects of phase composition; pHs; crude loading and additional neutral salt (NaCl). The hydrophilic ectoine was targeted to partition to the hydrophilic salt-rich phase. A total yield (YB) of 96.32% ± 1.08 of ectoine was obtained with ILABS of phase composition of 20% (w/w) (Bmim)BF4 and 30% (w/w) sulfate salts; system pH of 5.5 when the 20% (w/w) of crude feedstock was applied to the ILABS. There was no significant enhancement on the ectoine recovery efficiency using the ILABS when NaCl was added, therefore the ILABS composition without the additional neutral salt was recommended for the primary purification of ectoine. Partition coefficient (KE) of 30.80 ± 0.42, purity (PE) of 95.82% and enrichment factor (Ef) of 1.92 were recorded with the optimum (Bmim)BF4/sulfate ILABS. These findings have provided an insight on the feasibility of recovery of intracellular biomolecules using the green solvent-based aqueous system in one single-step operation.
Expression of His-tagged NADPH-dependent acetoacetyl-CoA reductase in recombinant Escherichia coli BL-21(DE3)

Kee PE, Chiang YC, Ng HS, Lan JC

J Biosci Bioeng, 2023 Oct;136(4):312-319.
PMID: 37500302 DOI: 10.1016/j.jbiosc.2023.07.001

Poly-3-hydroxybutyrate (P(3HB)), a member of the polyhydroxyalkanoate (PHA) family, is a biodegradable polyester with diverse industrial applications. NADPH-dependent acetoacetyl-CoA reductase (phaB) is the enzyme which plays an essential role in P(3HB) synthesis by catalyzing the conversion of the intermediates. The expression of phaB enzyme using the recombinant Escherichia coli BL-21(DE3) and the purification of the synthesized enzyme were studied. The pET-B3 plasmid harbouring the phaB gene derived from Ralstonia eutropha H16, was driven by the lac promoter in E. coli BL-21(DE3). The enzyme was expressed with different induction time, temperatures and cell age. Results showed that the cell age of 4 h, induction time of 12 h at 37°C were identified as the optimal conditions for the enzyme reductase expression. A specific activity of 0.151 U mg-1 protein and total protein concentration of 0.518 mg mg-1 of dry cell weight (DCW) were attained. Affinity chromatography was performed to purify the His-tagged phaB enzyme, in which enhanced the specific activity (14.44 U mg-1) and purification fold (38-fold), despite relative low yield (44.6%) of the enzyme was obtained. The purified phaB showed an optimal enzyme activity at 30°C and pH 8.0. The findings provide an alternative for the synthesis of the reductase enzyme which can be used in the industrial-scale production of the biodegradable polymers.
Clinical characteristics of ulcerative colitis in Singapore, a multiracial city-state

Ling KL, Ooi CJ, Luman W, Cheong WK, Choen FS, Ng HS

J Clin Gastroenterol, 2002 Aug;35(2):144-8.
PMID: 12172359

Ulcerative colitis (UC) is rare in Asia. Singapore is an ethnically heterogeneous city-state with a population made up of Chinese (77%), Indians (7.5%), and Malays (14%). This study describes and compares the characteristics of Chinese, Malay, and Indian patients with UC.
Influence of freeze-drying and spray-drying preservation methods on survivability rate of different types of protectants encapsulated Lactobacillus acidophilus FTDC 3081

Tang HW, Abbasiliasi S, Murugan P, Tam YJ, Ng HS, Tan JS

Biosci Biotechnol Biochem, 2020 Sep;84(9):1913-1920.
PMID: 32448058 DOI: 10.1080/09168451.2020.1770572

The aims of this study were to compare the effectiveness of different drying methods and to investigate the effects of adding a series of individual protectant such as skim milk, sucrose, maltodextrin, and corn starch for preserving Lactobacillus acidophilus FTDC 3081 cells during spray and freeze-drying and storage at different temperatures. Results showed a remarkable high survival rate of 70-80% immediately after spray- and freeze-drying in which the cell viability retained at the range of 109 to 1010 CFU/mL. After a month of storage, maltodextrin showed higher protective ability on both spray- and freeze-dried cells as compared to other protective agents at 4°C, 25°C, and 40°C. A complete loss in viability of spray-dried L. acidophilus FTDC 3081 was observed after a month at 40°C in the absence of protective agent.
Fulltext Nutrients for Prevention of Macular Degeneration and Eye-Related Diseases

Khoo HE, Ng HS, Yap WS, Goh HJH, Yim HS

Antioxidants (Basel), 2019 Apr 02;8(4).
PMID: 30986936 DOI: 10.3390/antiox8040085

The risk of macular degeneration can be reduced through the consumption of antioxidant-rich foods, supplements, and nutraceutical formulas. This review focuses on the antioxidants, vitamins, and minerals that have been reported for reducing the risk of macular degeneration and other eye-related diseases. Antioxidants including anthocyanins, carotenoids, flavonoids, and vitamins have been shown to reduce the risk of eye-related diseases. Anthocyanins extracted from berries are powerful antioxidants. Cyanidin, delphinidin, malvidin, pelargonidin, peonidin, and petunidin are anthocyanin aglycones detected in berries, currants, and other colored fruits and vegetables. β-Carotene, as well as xanthophyll lutein and zeaxanthin, have been reported to reduce the risk of macular degeneration. Flavonoids from plants help in the prevention of eye-related diseases through anti-inflammatory mechanisms. A combination of these antioxidants, vitamins, and minerals possess a synergistic effect on the prevention or risk reduction of macular degeneration. Formulas have been developed as dietary supplements to cater to the high demand from consumers and patients with eye problems. Many of the formulated dietary supplements that are sold in the market have been clinically proven for their efficacy to treat eye diseases. Although the bioactivities in the supplement capsules or tablets have been scientifically established for reducing risks of several diseases, which include macular degeneration and other eye-related diseases, knowledge on the right dosage, efficacy, and bioavailability of antioxidants, vitamins, and minerals is important for consumers. The information may help them make the best decision in choosing the right dietary supplements and nutraceuticals following the evidence-based recommended dosages and reference intakes for improving general health and preventing eye-related diseases. This review covers the potential causal factors involved in eye diseases, clinically proven treatments, and controversial findings on the antioxidants in the prevention of macular degeneration. Future studies should consider multiethnic and multicenter trials for eliminating potential bias in research.
Characterization of alcohol/salt aqueous two-phase system for optimal separation of gallic acids

Ng HS, Kee PE, Yim HS, Tan JS, Chow YH, Lan JC

J Biosci Bioeng, 2021 May;131(5):537-542.
PMID: 33674222 DOI: 10.1016/j.jbiosc.2021.01.004

Gallic acid (GA) is a hydrophilic polyphenol which is noteworthy for strong antioxidant capacity. The drawbacks of conventional extraction approaches such as time-consuming and high processing cost are often viewed as a hurdle to extract GA from plant sources in industrial scale. Aqueous two-phase system (ATPS) is a separation approach which can be employed as an alternative to the conventional approaches. The partition behaviour of GA in an alcohol/salt ATPS was investigated in this study to aid the development of industrial scale ATPS to extract GA from natural sources. The separation of GA was characterized by determining the types of alcohol and salt, phase composition, sample load, pH of the system and addition of adjuvants applied in the alcohol/salt ATPS construction. The hydrophilic GA was targeted to the salt-rich phase of the alcohol/salt ATPS with a partition coefficient (KGA) of 25.00 ± 0.00. The optimum condition of ATPS for the maximum partition of GA was achieved in ATPS comprised of 24% (w/w) 1-propanol and 22% (w/w) phosphate salt at pH 8 with 5% (w/w) of 1 mg/mL sample loading and 2% (w/w) NaCl addition. The findings suggest that ATPS can be applied for separation of GA from various natural sources.
Direct recovery of mangostins from Garcinia mangostana pericarps using cellulase-assisted aqueous micellar biphasic system with recyclable surfactant

Ng HS, Tan GYT, Lee KH, Zimmermann W, Yim HS, Lan JC

J Biosci Bioeng, 2018 Oct;126(4):507-513.
PMID: 29764763 DOI: 10.1016/j.jbiosc.2018.04.008

The α- and γ-mangostins from Garcinia mangostana pericarps (GMP) exhibit antioxidant, anti-bacterial, anti-inflammatory and anti-tumor properties. The extraction yields α- and γ-mangostins are often limited by the presence of the GMP cell walls. Therefore, the extraction and recovery of mangostins from GMP with an Aspergillus niger cellulase-assisted aqueous micellar biphasic system (CA-AMBS) was developed for enhanced yield of mangostins. Effects of the concentration of cellulase, the incubation time and the temperature of the system on the recovery of mangostins were investigated. The optimum condition for the recovery of α- and γ-mangostins was obtained with the addition of 0.5% (w/w) cellulase incubated at 40°C for 2 h. High log partition coefficients of α-mangostins (log Kα 4.79 ± 0.02) and γ-mangostins (log Kγ 4.02 ± 0.02) were achieved. High yields of α-mangostins (73.4%) and γ-mangostins (14.0%) were obtained from the micelle-rich bottom phase with final concentrations of 3.67 mg/mL and 0.70 mg/mL, respectively. The back-extraction of mangostins was performed with the addition of 30% (w/w) of isopropanol and 0.05 M of KCl at pH 9 to the bottom phase of the CA-AMBS. The yields of the α- and γ-mangostins from GMP were considerably enhanced with the CA-AMBS and the direct recovery of mangostins was demonstrated without additional downstream processing steps.
Partition efficiency of cytochrome c with alcohol/salt aqueous biphasic flotation system

Ng HS, Ng TC, Kee PE, Tan JS, Yim HS, Lan JC

J Biosci Bioeng, 2020 Feb;129(2):237-241.
PMID: 31629635 DOI: 10.1016/j.jbiosc.2019.08.013

Aqueous biphasic flotation (ABF) integrates aqueous biphasic system (ABS) and solvent sublation for recovery of target biomolecules. The feasibility of the alcohol/salt ABF for exclusive partition of cytochrome c to one specific phase of the system was investigated. Aliphatic alcohols of different carbon chain length (ethanol, 1-propanol and 2-propanol) and salts (sulfate, phosphate and citrate) were used for the phase formation. The effects of phase composition, concentration of sample loading, pH, flotation time and flow rate of the system on the partition efficiency of cytochrome c were determined. Cytochrome c was exclusively partitioned to the alcohol-rich top phase of the ABF of 18% (w/w) ethanol and 26% (w/w) ammonium sulfate with pH 6 and 20% (w/w) of sample loading. Highest partition coefficient (K) of 6.85 ± 0.21 and yield (YT) of 99.40% ± 0.02 were obtained with optimum flotation rate of 10 mL/min and flow rate of 10 min.
Efficiency of Ionic Liquids-Based Aqueous Two-phase Electrophoresis for Partition of Cytochrome c

Kee PE, Lan JC, Yim HS, Tan JS, Chow YH, Ng HS

Appl Biochem Biotechnol, 2020 May;191(1):376-386.
PMID: 31907777 DOI: 10.1007/s12010-019-03202-y

Cytochrome c is a small water-soluble protein that is abundantly found in the mitochondrial intermembrane space of microorganism, plants and mammalians. Ionic liquids (ILs)-based aqueous two-phase electrophoresis system (ATPES) was introduced in this study to investigate the partition efficiency of cytochrome c to facilitate subsequent development of two-phase electrophoresis for the separation of cytochrome c from microbial fermentation. The 1-Hexyl-3-methylimidazolium bromide, (C6mim)Br and potassium citrate salt were selected as the phase-forming components. Effects of phase composition; position of electrodes; pH and addition of neutral salt on the partition efficiency of cytochrome c in the ATPES were evaluated. Highest partition coefficient (K = 179.12 ± 0.82) and yield of cytochrome c in top phase (YT = 99.63% ± 0.00) were recorded with IL/salt ATPES composed of 30% (w/w) (C6mim)Br and 20% (w/w) potassium citrate salt of pH 7 and 3.0% (w/w) NaCl addition with anode at the bottom phase and cathode at the top phase. The SDS-PAGE profile revealed that cytochrome c with a molecular weight of 12 kDa was preferably partitioned to the IL-rich top phase. Present findings suggested that the single-step ATPES is a potential separation approach for the recovery of cytochrome c from microbial fermentation. Graphical Abstract.
Recent advances on the sustainable approaches for conversion and reutilization of food wastes to valuable bioproducts

Ng HS, Kee PE, Yim HS, Chen PT, Wei YH, Chi-Wei Lan J

Bioresour Technol, 2020 Apr;302:122889.
PMID: 32033841 DOI: 10.1016/j.biortech.2020.122889

The increasing amounts of food wastage and accumulation generated per annum due to the growing human population worldwide often associated with environmental pollution issues and scarcity of natural resources. In view of this, science community has worked towards in finding sustainable approaches to replace the common practices for food waste management. The agricultural and food processing wastes rich in nutrients are often the attractive substrates for the bioconversion for valuable bioproducts such as industrial enzymes, biofuel and bioactive compounds. The sustainable approaches on the re-utilization of food wastes as the industrial substrates for production of valuable bioproducts has meet the goals of circular bioeconomy, results in the diversify applications and increasing market demands for the bioproducts. This review discusses the current practice and recent advances on reutilization of food waste for bioconversion of valuable bioproducts from agricultural and food processing wastes.
Surfactant as an Additive for the Recovery of Potent Antioxidants from Garcinia mangostana Pericarps Using a Polymer/Salt Aqueous Biphasic System

Ng HS, Kee PE, Tan GY, Yim HS, Lan JC

Appl Biochem Biotechnol, 2020 May;191(1):273-283.
PMID: 32335865 DOI: 10.1007/s12010-020-03284-z

Garcinia mangostana pericarp is a good source of natural antioxidants with numerous functional properties. The conventional approaches for the recovery of antioxidants from Garcinia mangostana pericarp require long processing time and high temperature, which may cause degradation or loss of bioactivity of antioxidants, and often result in low recovery efficiency. In this study, the extraction of antioxidants from Garcinia mangostana pericarp was investigated using a polyethylene glycol (PEG)/citrate aqueous biphasic system (ABS) with the addition of surfactants. The optimum condition for the recovery of antioxidants was achieved in PEG 1000/citrate ABS of pH 8 with tie-line length (TLL) of 48.3% (w/w), volume ratio (VR) of 1.6, 0.2% (w/w) sample loading and addition of 1.0% (w/w) Tween 85. The antioxidants were recovered in the PEG-rich top phase with a high K value of 18.23 ± 0.33 and a recovery yield of 92.01% ± 0.09. The findings suggested that the addition of surfactants to polymer/salt ABS can enhance the recovery of antioxidants from Garcinia mangostana pericarps by conserving the antioxidative properties.
Enhanced recovery of astaxanthin from recombinant Kluyveromyces marxianus with ultrasonication-assisted alcohol/salt aqueous biphasic system

Ng HS, Kee PE, Wu YC, Chen L, Wong SYW, Lan JC

J Biosci Bioeng, 2021 Nov;132(5):513-518.
PMID: 34479804 DOI: 10.1016/j.jbiosc.2021.07.004

Microbial astaxanthin with strong antioxidant activity is greatly demanded for diverse applications. Extractive disruption in aqueous biphasic system (ABS) integrates the cells disruption and biomolecules recovery processes in one-step operation, allowing the direct recovery of intracellular biomolecules with biphasic system upon released from cells. In this study, astaxanthin was recovered from recombinant Kluyveromyces marxianus yeast cells via extractive disruption using alcohol/salt ABS. Recombinant K. marxianus yeast is engineered to produce high concentration of free form astaxanthin. Highest partition coefficient (K = 90.02 ± 2.25) and yield (Y = 96.80% ± 0.05) of astaxanthin were obtained with ABS composed of 20% (w/w) 1-propanol and 20% (w/w) sodium citrate of pH 5, 0.5% (w/w) yeast cells loading and additional of 1% (w/w) 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim)BF4 to improve the migration of astaxanthin to alcohol-rich top phase. The incorporation of 2.5 h of ultrasonication to the biphasic system further enhanced the astaxanthin recovery in ABS. The direct recovery of astaxanthin from recombinant K. marxianus cells was demonstrated with the ultrasonication-assisted alcohol/salt ABS which integrates the extraction and concentration of astaxanthin in a single-step operation.
Fulltext Extraction behaviors of aqueous PEG impregnated resin system in terms of impregnation stability and recovery via protein impregnated resin interactions on bovine serum albumin

Abdul Aziz NFH, Abbasiliasi S, Abu Zarin M, Ng HS, Lan C, Tan JS

PeerJ, 2021;9:e11920.
PMID: 34963820 DOI: 10.7717/peerj.11920

Background: Current advances in biotechnology have been looked at as alternative approaches towards the limited product recovery due to time- and cost-consuming drawbacks on the conventional purification methods. This study aimed to purify bovine serum albumin (BSA) as an exemplary target product using an aqueous impregnated resin system (AIRS). This method implies the concept of hydrophobicity of polymer that impregnated into the resins and driven by electrostatic attractions and hydrophilicity of aqueous salt solution to extract the target product.
Methods: The extraction behaviors of impregnation in terms of stability and adsorption kinetics via protein-aqueous polymer impregnated resin were studied. Impregnation stability was determined by the leaching factor of polyethylene glycol (PEG). The major factors such as PEG molecular weights and concentration, pH of aqueous salt solution, extraction methods (sonication and agitation) and types of adsorbent material and concentration of aqueous salt phase influencing on partitioning of biomolecule were also investigated.
Results: For impregnation stability, the leaching factor for Amberlite XAD4 did not exceed 1%. The scanning electron microscopy (SEM) image analysis of Amberlite XAD4 attributes the structural changes with impregnation of resins. For adsorption kinetics, Freundlich adsorption isotherm with the highest R2 value (0.95) gives an indication of favorable adsorption process. Performance of AIRS impregnated with 40% (w/w) of PEG 2000 was found better than aqueous-two phase system (ATPS) by yielding the highest recovery of BSA (53.72%). The outcomes of this study propound the scope for the application of AIRS in purification of biomolecules.

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