Displaying publications 1 - 20 of 60 in total

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  1. 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.
  2. Ting TY, Li Y, Bunawan H, Ramzi AB, Goh HH
    J Biosci Bioeng, 2023 Apr;135(4):259-265.
    PMID: 36803862 DOI: 10.1016/j.jbiosc.2023.01.010
    Saccharomyces cerevisiae has a long-standing history of biotechnological applications even before the dawn of modern biotechnology. The field is undergoing accelerated advancement with the recent systems and synthetic biology approaches. In this review, we highlight the recent findings in the field with a focus on omics studies of S. cerevisiae to investigate its stress tolerance in different industries. The latest advancements in S. cerevisiae systems and synthetic biology approaches for the development of genome-scale metabolic models (GEMs) and molecular tools such as multiplex Cas9, Cas12a, Cpf1, and Csy4 genome editing tools, modular expression cassette with optimal transcription factors, promoters, and terminator libraries as well as metabolic engineering. Omics data analysis is key to the identification of exploitable native genes/proteins/pathways in S. cerevisiae with the optimization of heterologous pathway implementation and fermentation conditions. Through systems and synthetic biology, various heterologous compound productions that require non-native biosynthetic pathways in a cell factory have been established via different strategies of metabolic engineering integrated with machine learning.
  3. Saleena LAK, Teo MYM, How YH, In LLA, Pui LP
    J Biosci Bioeng, 2023 Jan;135(1):1-9.
    PMID: 36428209 DOI: 10.1016/j.jbiosc.2022.10.010
    Fermented foods are gaining popularity due to health-promoting properties with high levels of nutrients, phytochemicals, bioactive compounds, and probiotic microorganisms. Due to its unique fermentation process, Lactococcus lactis plays a key role in the food business, notably in the manufacturing of dairy products. The superior biological activities of L. lactis in these functional foods include anti-inflammatory and immunomodulatory capabilities. L. lactis boosted growth performance, controlled amino acid profiles, intestinal immunology, and microbiota. Besides that, the administration of L. lactis increased the rate of infection clearance. Innate and acquired immune responses would be upregulated in both local and systemic compartments, resulting in these consequences. L. lactis is often employed in the food sector and is currently being exploited as a delivery vehicle for biological research. These bacteria are being eyed as potential candidates for biotechnological applications. With this in mind, we reviewed the immunomodulatory effects of different L. lactis strains.
  4. Sakai K, Hassan MA, Vairappan CS, Shirai Y
    J Biosci Bioeng, 2022 Feb 09.
    PMID: 35151536 DOI: 10.1016/j.jbiosc.2022.01.001
    Palm oil is a representative and important biomass, not only as the most edible vegetable oil consumed worldwide, but also as a material for chemicals and biofuels. Despite the potential sustainability of the palm oil industry, it has conventionally emitted excess greenhouse gases, waste materials, and wastewater, brought land use change, thus affecting the natural environment. Therefore, the successful development of a sustainable palm oil industry is a touchstone for promoting the bioeconomy. Here, we first review the concept of the bioeconomy and the positive and negative aspects of the palm oil industry. Then, we consider solutions for introducing a green economy into the palm oil industry, such that it may coexist with biodiversity and environmental conservation toward the Sustainable Development Goals.
  5. Zainul Kamal S, Ngoc Minh Tran Q, Koyama M, Mimoto H, Asada C, Nakamura Y, et al.
    J Biosci Bioeng, 2022 Jan 31.
    PMID: 35115228 DOI: 10.1016/j.jbiosc.2022.01.004
    Hydrothermal treatment (HTT) as a pretreatment method for compost raw material has multiple benefits such as enhanced solubility of organic material, improved bioaugmentation, and reduced biohazard by killing harmful microorganisms. In this study, we pretreated food waste via HTT at 180 °C for 30 min to investigate its effect on food waste composting. HTT generated 8.98 mg/g-dry solid (g-ds) of 5-hydroxymethylfurfural and 4.32 mg/g-ds furfural. These furan compounds were completely decomposed in the early stage of composting, subsequently the organic matter in the food waste started to be degraded. The HTT-pretreated experiment demonstrated less organic matter degradation during composting as well as lower compost phytotoxicity compared to the non-HTT-pretreated experiment, where the conversion of carbon was 25.2% and the germination index value was 55%. HTT probably denatured part of the organic matter and making it more difficult to decompose, thereby preventing the rapid release of high concentrations of phytotoxic compounds such as organic acids and ammonium ions during composting. High-throughput microbial community analysis revealed that only Firmicutes appeared in the HTT-pretreated experiment, however, other bacterial groups also appeared in the non-HTT-pretreated experiment. This was possibly influenced by furan compounds and the changes of easily degradable organic matter to hardly degradable. Bacillus and Lysinibacillus were dominant in both composting experiments during vigorous organic matter degradation, suggesting that these bacterial groups were the main contributors to food waste composting. This study suggests that HTT is advantageous for the pretreatment of easily degradable food waste, as compost with less phytotoxicity was produced.
  6. 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.
  7. Yang J, Lu J, Zhu Q, Tao Y, Zhu Q, Guo C, et al.
    J Biosci Bioeng, 2021 Aug;132(2):161-166.
    PMID: 33972168 DOI: 10.1016/j.jbiosc.2020.12.016
    As one of Lianyungang's most famous specialties, Acanthogobius hasta is delicious and nutritious fish, but is extremely susceptible to spoilage during transportation and storage. In this study, Lactobacillus plantarum MMB-07 was isolated from traditional fermented sour fish to reduce losses and improve the utilization and food value of A. hasta. L. plantarum MMB-07 had good ability of acid production and acid resistance. Moreover, it could also inhibit common pathogens in food or aquatic products to ensure the safety of fermented products. MMB-07 was used to ferment A. hasta and obtain fermented Suanyu rich in nutrition value and good flavor. The volatile base nitrogen was 18.44 mg/100 g and the fermented fish meat maintained second-grade freshness. Thiobarbituric acid assay was 0.90 mg/kg and fat in fish meat was oxidized to a low degree. The studies indicated that MMB-07 has a high application prospect in low salt fermented fish.
  8. Mohamad-Zainal NSL, Ramli N, Zolkefli N, Mustapha NA, Hassan MA, Maeda T
    J Biosci Bioeng, 2021 Aug;132(2):174-182.
    PMID: 34074597 DOI: 10.1016/j.jbiosc.2021.04.014
    Alcaligenaceae and Chromatiaceae were previously reported as the specific pollution bioindicators in the receiving river water contaminated by palm oil mill effluent (POME) final discharge. Considering the inevitable sensitivity of bacteria under environmental stresses, it is crucial to assess the survivability of both bacteria in the fluctuated environmental factors, proving their credibility as POME pollution bioindicators in the environment. In this study, the survivability of Alcaligenaceae and Chromatiaceae from facultative pond, algae (aerobic) pond and final discharge were evaluated under varying sets of temperature (25-40°C), pH (pH 7-9) and low/high total suspended solid (TSS) contents of POME collected during low/high crop seasons of oil palm, respectively. Following treatment, the viability status and compositions of the bacterial community were assessed using flow cytometry-based assay and high-throughput Illumina MiSeq, respectively, in correlation with the changes of physicochemical properties. The changes in temperature, pH and TSS indeed changed the physicochemical properties of POME. The functionality of bacterial cells was also shifted where the viable cells and high nucleic acid contents reduced at elevated levels of temperature and pH but increased at high TSS content. Interestingly, the Alcaligenaceae and Chromatiaceae continuously detected in the samples which accounted for more than 0.5% of relative abundance, with a positive correlation with biological oxygen demand (BOD5) concentration. Therefore, either Alcaligenaceae or Chromatiaceae or both could be regarded as the reliable and specific bacterial indicators to indicate the pollution in river water due to POME final discharge despite the fluctuations in temperature, pH and TSS.
  9. 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.
  10. Abdul Aziz FA, Suzuki K, Honjo M, Amano K, Mohd Din ARJB, Tashiro Y, et al.
    J Biosci Bioeng, 2021 Jan;131(1):77-83.
    PMID: 33268319 DOI: 10.1016/j.jbiosc.2020.09.009
    The coexisting mechanism of a synthetic bacterial community (SBC) was investigated to better understand how to manage microbial communities. The SBC was constructed with three kinds of phenol-utilizing bacteria, Pseudomonas sp. LAB-08, Comamonas testosteroni R2, and Cupriavidus sp. P-10, under chemostat conditions supplied with phenol as a sole carbon and energy source. Population densities of all strains were monitored by real-time quantitative PCR (qPCR) targeting the gene encoding the large subunit of phenol hydroxylase. Although the supply of phenol was stopped to allow perturbation in the SBC, all of the strains coexisted and the degradation of phenol was maintained for more than 800 days. The qPCR analyses showed that strains LAB-08 and R2 became dominant simultaneously, whereas strain P-10 was a minor population. This phenomenon was observed before and after the phenol-supply stoppage. The kinetic parameters for phenol of the SBC changed before and after the phenol-supply stoppage, which suggests a change in functional roles of strains in the SBC. Transcriptional levels of phenol hydroxylase and catechol dioxygenases of three strains were monitored by reverse-transcription qPCR (RT-qPCR). The RT-qPCR analyses revealed that all strains shared phenol and survived independently before the phenol-supply stoppage. After the stoppage, strain P-10 would incur the cost for degradation of phenol and catechol, whereas strains LAB-08 and R2 seemed to be cheaters using metabolites, indicating the development of the metabolic network. These results indicated that it is important for the management and redesign of microbial communities to understand the metabolism of bacterial communities.
  11. 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.
  12. 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.
  13. 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.
  14. Jiao L, Chi H, Lu Z, Zhang C, Chia SR, Show PL, et al.
    J Biosci Bioeng, 2020 Jun;129(6):672-678.
    PMID: 32088137 DOI: 10.1016/j.jbiosc.2020.01.007
    l-Asparaginases have the potential to inhibit the formation of acrylamide, a harmful toxin formed during high temperature processing of food. A novel bacterium which produces l-asparaginase was screened. Type I l-asparaginase gene from Acinetobacter soli was cloned and expressed in Escherichia coli. The recombinant l-asparaginase had an activity of 42.0 IU mL-1 and showed no activity toward l-glutamine and d-asparagine. The recombinant l-asparaginase exhibited maximum catalytic activity at pH 8.0 and 40°C. The enzyme was stable in the pH ranging from 6.0 to 9.0. The activity of the recombinant enzyme was substantially enhanced by Ba2+, dithiothreitol, and β-mercaptoethanol. The Km and Vmax values of the l-asparaginase for the l-asparagine were 3.22 mmol L-1 and 1.55 IU μg-1, respectively. Moreover, the recombinant l-asparaginase had the ability to mitigate acrylamide formation in potato chips. Compared with the untreated group, the content of acrylamide in samples treated with the enzyme was effectively decreased by 55.9%. These results indicate that the novel type I l-asparaginase has the potential for application in the food processing industry.
  15. Lu J, Zhang C, Leong HY, Show PL, Lu F, Lu Z
    J Biosci Bioeng, 2020 Mar;129(3):327-332.
    PMID: 31585857 DOI: 10.1016/j.jbiosc.2019.09.006
    In this study, the bacterial lipoxygenase (LOX) gene from Pseudomonas aeruginosa ATCC27853 (pse-LOX) was cloned, sequenced and heterologous expressed in Escherichia coli by auto-induction expression strategy. Production of the recombinant pse-LOX (pse-rLOX) gene up to 23,850 U/mL (264 mg pure protein/L bacterial culture fluid) was observed in the end of this process. To the best of our knowledge, this is the first attempt to manipulate LOX heterologous expression process using auto-induction expression approach, and it is the highest production of recombinant LOX compared with other reports. Subsequently, the resulted pse-rLOX was proved to efficiently degrade triphenylmethane dyes such as malachite green, brilliant green and aniline blue. Generally, an overproduction of the LOX from P. aeruginosa was observed in E. coli, and this recombinant gene is a potential candidate as biocatalyst for triphenylmethane dyes decolorization.
  16. 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.
  17. Krishnamoorthy R, Govindan B, Banat F, Sagadevan V, Purushothaman M, Show PL
    J Biosci Bioeng, 2019 Jul;128(1):88-97.
    PMID: 30679113 DOI: 10.1016/j.jbiosc.2018.12.011
    Phosphoric acid impregnated activated carbon from date pits (DPAC) was prepared through single step activation. Prepared DPAC was studied for its structural, elemental, chemical, surface and crystal nature. Adsorption ability of the DPAC was assessed through divalent lead ions separation studies. Effect of adsorbent dosage, contact time, pH, operating temperature and initial feed concentration on lead removal by DPAC was studied. Maximum Pb(II) adsorption capacity of 101.35 mg/g was attained for a contact time of 30 min and pH of 6 at 30°C. Increase in initial feed concentration enhanced the adsorption ability of DPAC and the rise in adsorbent dosage resulted in improved Pb(II) removal efficiency. Thermodynamic studies revealed that the lead adsorption on DPAC was exothermic and instantaneous in nature. Kinetic and equilibrium studies confirmed the suitability of pseudo-second order and Langmuir isotherm for divalent lead ions binding on DPAC. Reusability studies showed that HCl was the effective regeneration medium and the DPAC could be reused for a maximum of 4 times with slight reduction in Pb(II) removal efficiency (<10%). Results indicated the promising use of date pits biomass as a low cost and efficient starting material to prepare activated carbon for divalent lead ions removal.
  18. Juanssilfero AB, Kahar P, Amza RL, Yopi, Sudesh K, Ogino C, et al.
    J Biosci Bioeng, 2019 Jun;127(6):726-731.
    PMID: 30642786 DOI: 10.1016/j.jbiosc.2018.12.002
    The ability of oleaginous yeast Lipomyces starkeyi to efficiently produce lipids when cultivated on sap extracted from felled oil palm trunk (OPT) as a novel inexpensive renewable carbon source was evaluated. OPT sap was found to contain approximately 98 g/L glucose and 32 g/L fructose. Batch fermentations were performed using three different OPT sap medium conditions: regular sap, enriched sap, and enriched sap at pH 5.0. Under all sap medium conditions, the cell biomass and lipid production achieved were approximately 30 g/L and 60% (w/w), respectively. L. starkeyi tolerated acidified medium (initial pH ≈ 3) and produced considerable amounts of ethanol as well as xylitol as by-products. The fatty acid profile of L. starkeyi was remarkably similar to that of palm oil, one of the most common vegetable oil feedstock used in biodiesel production with oleic acid as the major fatty acid followed by palmitic, stearic and linoleic acids.
  19. Ragab TIM, Malek RA, Elsehemy IA, Farag MMS, Salama BM, Abd El-Baseer MA, et al.
    J Biosci Bioeng, 2019 Jun;127(6):655-662.
    PMID: 30795878 DOI: 10.1016/j.jbiosc.2018.09.008
    This study focused on kinetics of levan yield by Bacillus subtilis M, in a 150 L stirred tank bioreactor under controlled pH conditions. The optimized production medium was composed of (g/L): commercial sucrose 100.0, yeast extract 2.0, K2HPO4 3.0 and MgSO4⋅7H2O 0.2; an increase in both carbohydrates consumption and cell growth depended on increasing the size of the stirred tank bioreactor from 16 L to 150 L. The highest levansucrase production (63.4 U/mL) and levan yield of 47 g/L was obtained after 24 h. Also, the specific levan yield (Yp/x) which reflects the cell productivity increased with the size increase of the stirred tank bioreactor and reached its maximum value of about 29.4 g/g cells. These results suggested that B. subtilis M could play an important role in levan yield on a large scale in the future. Chemical modifications of B. subtilis M crude levan (CL) into sulfated (SL), phosphorylated (PL), and carboxymethylated levans (CML) were done. The difference in CL structure and its derivatives was detected by FT-IR transmission spectrum. The cytotoxicity of CL and its derivatives were evaluated by HepGII, Mcf-7 and CaCo-2. In general most tested levans forms had no significant cytotoxicity effect. In fact, the carboxymethylated and phosphrylated forms had a lower anti-cancer effect than CL. On the other hand, SL had the highest cytotoxicity showing SL had a significant anti-cancer effect. The results of cytotoxicity and cell viability were statistically analyzed using three-way ANOVA.
  20. Nguyen TDP, Tran TNT, Le TVA, Nguyen Phan TX, Show PL, Chia SR
    J Biosci Bioeng, 2019 Apr;127(4):492-498.
    PMID: 30416001 DOI: 10.1016/j.jbiosc.2018.09.004
    Nowadays, the pretreatment of wastewater prior to discharge is very important in various industries as the wastewater without any treatment contains high organic pollution loads that would pollute the receiving waterbody and potentially cause eutrophication and oxygen depletion to aquatic life. The reuse of seafood wastewater discharge in microalgae cultivation offers beneficial purposes such as reduced processing cost for wastewater treatment, replenishing ground water basin as well as financial savings for microalgae cultivation. In this paper, the cultivation of Chlorella vulgaris with an initial concentration of 0.01 ± 0.001 g⋅L-1 using seafood sewage discharge under sunlight and fluorescent illumination was investigated in laboratory-scale without adjusting mineral nutrients and pH. The ability of nutrient removal under different lighting conditions, the metabolism of C. vulgaris and new medium as well as the occurrence of auto-flocculation of microalgae biomass were evaluated for 14 days. The results showed that different illumination sources did not influence the microalgae growth, chemical oxygen demand (COD) and biochemical oxygen demand (BOD) significantly. However, the total nitrogen (total-N) and total phosphorus (total-P) contents of microalgae were sensitive to the illumination mode. The amount of COD, BOD, total-N and total-P were decreased by 88%, 81%, 95%, and 83% under sunlight mode and 81%, 74%, 79%, and 72% under fluorescent illumination, respectively. Furthermore, microalgae were auto-flocculated at the final days of cultivation with maximum biomass concentration of 0.49 ± 0.01 g⋅L-1, and the pH value had increased to pH 9.8 ± 0.1 under sunlight illumination.
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