Impact of immobilized algae and its consortium in biodegradation of the textile dyes

References

• Abd Ellatif S, El-Sheekh MM, Senousy HH. 2021. Role of microalgal ligninolytic enzymes in industrial dye decolorization. Int J Phytoremediation. 23(1):41–52. doi:10.1080/15226514.2020.1789842.
   PubMed Web of Science ®Google Scholar
• Abou El-Souod GW, El-Sheekh MM. 2016. Biodegradation of Basic Fuchsin and Methyl Red. Environ Eng Manag J. 15(2):279–286. doi:10.30638/eemj.2016.028.
   Google Scholar
• Acuner E, Dilek FB. 2004. Treatment of tectilon yellow 2G by Chlorella vulgaris. Process Biochem. 39(5):623–631. ‏ doi:10.1016/S0032-9592(03)00138-9.
   Web of Science ®Google Scholar
• Ahmad A, Mohd-Setapar SH, Chuong CS, Khatoon A, Wani WA, Kumar R, Rafatullah M. 2015. Recent advances in new generation dye removal technologies: novel search for approaches to reprocess wastewater. RSC Adv. 5(39):30801–30818. ‏ doi:10.1039/C4RA16959J.
   Web of Science ®Google Scholar
• Ahmed KF, Wang G, Silander J, Wilson AM, Allen JM, Horton R, Anyah R. 2013. Statistical downscaling and bias correction of climate model outputs for climate change impact assessment in the US northeast. Global Planet Change. 100:320–332. ‏ doi:10.1016/j.gloplacha.2012.11.003.
   Web of Science ®Google Scholar
• Ajaz M, Shakeel S, Rehman A. 2020. Microbial use for azo dye degradation—a strategy for dye bioremediation. Int Microbiol. 23(2):149–159. ‏ doi:10.1007/s10123-019-00103-2.
   PubMed Web of Science ®Google Scholar
• Aksu Z. 2005. Application of biosorption for the removal of organic pollutants: a review. Process Biochem. 40(3–4):997–1026. ‏ doi:10.1016/j.procbio.2004.04.008.
   Web of Science ®Google Scholar
• Aksu Z, Tezer S. 2005. Biosorption of reactive dyes on the green alga Chlorella vulgaris. Process Biochem. 40(3–4):1347–1361. ‏ doi:10.1016/j.procbio.2004.06.007.
   Web of Science ®Google Scholar
• Ali H. 2010. Biodegradation of synthetic dyes—a review. Water Air Soil Pollut. 213(1–4):251–273. ‏ doi:10.1007/s11270-010-0382-4.
   Web of Science ®Google Scholar
• Alketife AM, Judd S, Znad H. 2017. Synergistic effects and optimization of nitrogen and phosphorus concentrations on the growth and nutrient uptake of a freshwater Chlorella vulgaris. Environ Technol. 38(1):94–102. ‏ doi:10.1080/09593330.2016.1186227.
   PubMed Web of Science ®Google Scholar
• Aydin H, Baysal G. 2006. Adsorption of acid dyes in aqueous solutions by Pistacala khinjuk stocks. Desalination. 19:248–259.
   Google Scholar
• Bafana A, Devi SS, Chakrabarti T. 2011. Azo dyes: past, present and the future. Environ Rev. 19(NA):350–371. doi:10.1139/a11-018.
   Google Scholar
• Bertille BD, Catherine B, Simon MD. 2020. Effect of essential oil- and iodine treatments on the bacterial microbiota of the brown alga Ectocarpus siliculosus. J Appl Phycol. 33(1):459–470. doi:10.1007/s10811-020-02286-y.
   Google Scholar
• Cai T, Park SY, Li Y. 2013. Nutrient recovery from wastewater streams by microalgae: status and prospects. Renew Sustain Energy Rev. 19:360–369. ‏ doi:10.1016/j.rser.2012.11.030.
   Web of Science ®Google Scholar
• Chen M, Tang H, Ma H, Holland TC, Ng KS, Salley SO. 2011. Effect of nutrients on growth and lipid accumulation in the green algae Dunaliella tertiolecta. Bioresour Technol. 102(2):1649–1655. ‏ doi:10.1016/j.biortech.2010.09.062.
   PubMed Web of Science ®Google Scholar
• Chisti Y. 2007. Biodiesel from microalgae. Biotechnol Adv. 25(3):294–306. ‏ doi:10.1016/j.biotechadv.2007.02.001.
   PubMed Web of Science ®Google Scholar
• Chorvatova AM, Uherek M, Mateasik A, Chorvat D. 2020. Time-resolved endogenous chlorophyll fluorescence sensitivity to pH: study on Chlorella sp. algae. Methods Appl Fluoresc. 8(2):024007. ‏ doi:10.1088/2050-6120/ab77f4.
   PubMed Web of Science ®Google Scholar
• Chowdhury S, Mishra R, Saha P, Kushwaha P. 2011. Adsorption thermodynamics, kinetics and isosteric heat of adsorption of malachite green onto chemically modified rice husk. Desalination. 265(1–3):159–168. ‏ doi:10.1016/j.desal.2010.07.047.
   Web of Science ®Google Scholar
• Christopher J, Owen PW, Ajay S. 2002. Biodegradation of dimethyl phthalate with high removal rates in a packed-bed reactor. World J Microbiol Biotechnol. 18:7–10.
   Google Scholar
• Chu WL, See YC, Phang SM. 2009. Use of immobilized Chlorella vulgaris for the removal of colour from textile dyes. J Appl Phycol. 21(6):641–648. ‏ doi:10.1007/s10811-008-9396-3.
   Google Scholar
• Crini G. 2006. Non-conventional low-cost adsorbents for dye removal: a review. Bioresour Technol. 97(9):1061–1085. ‏ doi:10.1016/j.biortech.2005.05.001.
   PubMed Web of Science ®Google Scholar
• Daneshvar N, Ayazloo M, Khataee AR, Pourhassan M. 2007a. Biological decolorization of dye solution containing Malachite Green by microalgae Cosmarium sp. Bioresour Technol. 98(6):1176–1182. ‏ doi:10.1016/j.biortech.2006.05.025.
   PubMed Web of Science ®Google Scholar
• Daneshvar N, Khataee AR, Rasoulifard MH, Pourhassan M. 2007b. Biodegradation of dye solution containing Malachite Green: optimization of effective parameters using Taguchi method. J Hazard Mater. 143(1–2):214–219. ‏ doi:10.1016/j.jhazmat.2006.09.016.
   PubMed Web of Science ®Google Scholar
• De-Bashan LE, Bashan Y. 2010. Immobilized microalgae for removing pollutants: review of practical aspects. Bioresour Technol. 101(6):1611–1627. ‏ doi:10.1016/j.biortech.2009.09.043.
   PubMed Web of Science ®Google Scholar
• Deivasigamani C, Das N. 2011. Biodegradation of Basic Violet 3 by Candida krusei isolated from textile wastewater. Biodegradation. 22(6):1169–1180. ‏ doi:10.1007/s10532-011-9472-2.
   PubMed Web of Science ®Google Scholar
• Dong H, Guo T, Zhang W, Ying H, Wang P, Wang Y, Chen Y. 2019. Biochemical characterization of a novel azoreductase from Streptomyces sp.: application in eco-friendly decolorization of azo dye wastewater. Int J Biol Macromol. 140:1037–1046. ‏ doi:10.1016/j.ijbiomac.2019.08.196.
   PubMedGoogle Scholar
• El-Sheekh MM, Abou-El-Souod GW, El Asrag HA. 2017. Biodegradation of some dyes by the cyanobacteria species Pseudoanabaena sp. and Microcystis aeruginosa Kützing. Egypt J Exp Biol. 13(2):233–243.
   Google Scholar
• El-Sheekh MM, Abou-El-Souod GW, El Asrag HA. 2018. Biodegradation of some dyes by the green alga Chlorella vulgaris and the cyanobacterium Aphanocapsa elachista. Egypt J Bot. 58(3):311–320. ‏doi:10.21608/ejbo.2018.2675.1145.
   Google Scholar
• El-Sheekh MM, El-Shanshoury AR, Abou-El-Souod GW, Gharieb DY, El Shafay SM. 2021. Decolorization of dyestuffs by some species of green algae and cyanobacteria and its consortium. Int J Environ Sci Technol. 18:3895–3906. doi:10.1007/s13762-020-03108-x.
   Google Scholar
• El-Sheekh MM, Gharieb MM, Abou-El-Souod GW. 2009. Biodegradation of dyes by some green algae and cyanobacteria. Int Biodeterior Biodegrad. 63(6):699–704. ‏ doi:10.1016/j.ibiod.2009.04.010.
   Web of Science ®Google Scholar
• Ergene A, Ada K, Tan S, Katırcıoğlu H. 2009. Removal of Remazol Brilliant Blue R dye from aqueous solutions by adsorption onto immobilized Scenedesmus quadricauda: equilibrium and kinetic modeling studies. Desalination. 249(3):1308–1314. ‏ doi:10.1016/j.desal.2009.06.027.
   Web of Science ®Google Scholar
• Ertugrul M, Hegde S. 2008. Board compensation practices and agency costs of debt. J Corporate Finance. 14(5):512–531. ‏ doi:10.1016/j.jcorpfin.2008.09.004.
   Google Scholar
• FAO. 2014. http://www.fao.org/docrep/003/w3732e/w3732e06.htm#2.3.%20Algal%20production.
   Google Scholar
• Farag S, Bekhit F, Attia AM. 2016. Bacterial isolation, optimization and immobilization for decolorization and degradation of the azo dye (Basic Red 46). Res J Pharmaceut Biol Chem Sci. 7(4):1323–1335.
   Google Scholar
• Fu Y, Viraraghavan T. 2001. Fungal decolorization of dye wastewaters: a review. Bioresour Technol. 79(3):251–262. ‏ doi:10.1016/S0960-8524(01)00028-1.
   PubMed Web of Science ®Google Scholar
• Gao J, Zhang Q, Su K, Chen R, Peng Y. 2010. Biosorption of Acid Yellow 17 from aqueous solution by non-living aerobic granular sludge. J Hazard Mater. 174(1–3):215–225. ‏ doi:10.1016/j.jhazmat.2009.09.039.
   PubMed Web of Science ®Google Scholar
• Gimmler H. 2001. Acidophilic and acidotolerant algae. In: Algal adaptation to environmental stresses. Berlin; Heidelberg: Springer. p. 259–290.
   Google Scholar
• Gómez PI, González MA. 2005. The effect of temperature and irradiance on the growth and carotenogenic capacity of seven strains of Dunaliella salina (Chlorophyta) cultivated under laboratory conditions. Biological Res. 38(2–3):151–162.
   PubMedGoogle Scholar
• Hadibarata T, Nor NM. 2014. Decolorization and degradation mechanism of Amaranth by Polyporus sp. S133. Bioprocess Biosyst Eng. 37(9):1879–1885. ‏ doi:10.1007/s00449-014-1162-0.
   PubMedGoogle Scholar
• Hadibarata T, Yusoff ARM, Kristanti RA. 2012. Decolorization and metabolism of anthraquionone-type dye by laccase of white-rot fungi Polyporus sp. S133. Water Air Soil Pollut. 223(2):933–941. ‏ doi:10.1007/s11270-011-0914-6.
   Web of Science ®Google Scholar
• Hamouda RA, El-Naggar NE-A, Abou-El-Se GW. 2018. Enhancement of pharmaceutical and bioactive components of Scenedesmus obliquus grown using different concentrations of KNO3. Int J Pharmacol. 14(6):758–765. doi:10.3923/ijp.2018.758.765.
   Google Scholar
• Hassaan MA, El-Nemr A. 2017. Health and environmental impacts of dyes: mini review. Am J Environ Sci Eng. 1(3):64–67.
   Google Scholar
• Holkar CR, Jadhav AJ, Pinjari DV, Mahamuni NM, Pandit AB. 2016. A critical review on textile wastewater treatments: possible approaches. J Environ Manage. 182:351–366. ‏ doi:10.1016/j.jenvman.2016.07.090.
   PubMed Web of Science ®Google Scholar
• Ince NH, Tezcanlı́ G. 2001. Reactive dyestuff degradation by combined sonolysis and ozonation. Dyes Pigments. 49(3):145–153. ‏ doi:10.1016/S0143-7208(01)00019-5.
   Web of Science ®Google Scholar
• Jinqi L, Houtian L. 1992. Degradation of azo dyes by algae. Environ Pollut. 75(3):273–278. ‏ doi:10.1016/0269-7491(92)90127-V.
   PubMedGoogle Scholar
• Kaparapu J, Geddada MNR. 2016. Applications of immobilized algae. J Algal Biomass Util. 7(2):122–128.
   Google Scholar
• Kaur H, Ganguli D, Bachhawat AK. 2012. Glutathione degradation by the alternative pathway (DUG pathway) in Saccharomyces cerevisiae is initiated by (Dug2p-Dug3p) 2 complex, a novel glutamine amidotransferase (GATase) enzyme acting on glutathione. J Biol Chem. 287(12):8920–8931. ‏ doi:10.1074/jbc.M111.327411.
   PubMedGoogle Scholar
• Keith W, John W. 2008. PH and oxygen electrodes, principles and techniques of biochemistry and molecular biology. 6th ed. Cambridge: Cambridge University Press. p. 18–23.
   Google Scholar
• Khan TA, Dahiya S, Ali I. 2012. Removal of direct red 81 dye from aqueous solution by native and citric acid modified bamboo sawdust-kinetic study and equilibrium isotherm analyses. Gazi Univ J Sci. 25(1):59–87.
   Google Scholar
• Khan M, Malik R. 2016. Forced convective heat transfer to Sisko nanofluid past a stretching cylinder in the presence of variable thermal conductivity. J Mol Liquids. 218:1–7. ‏ doi:10.1016/j.molliq.2016.02.024.
   Google Scholar
• Kirrolia A, Bishnoi NR, Singh R. 2012. Effect of shaking, incubation temperature, salinity and media composition on growth traits of green microalgae Chlorococcum sp. J Algal Biomass Util. 3(3):46–53.
   Google Scholar
• Kiruthika S, Rajendran R. 2020. A review on bioremediation of a zo dyes using microbial consortium from different sources. Asian J Microbiol Biotech Environ Sci. 22(4):614–630.
   Google Scholar
• Kisand V, Tuvikene L, Nõges T. 2001. Role of phosphorus and nitrogen for bacteria and phytopankton development in a large shallow lake. Hydrobiologia. 457(1):187–197.
   Google Scholar
• Kourkoutas Y, Bekatorou A, Banat IM, Marchant R, Koutinas AA. 2004. Immobilization technologies and support materials suitable in alcohol beverages production: a review. Food Microbiol. 21(4):377–397. ‏ doi:10.1016/j.fm.2003.10.005.
   Web of Science ®Google Scholar
• Kuhl A. 1962. Zurphysiologie der Speicherung Kondensierteran organischer phosphate in Chlorella. Verlrag Bot Hrsg Deut Bot Ges. 1:157–166.
   Google Scholar
• Kumar A, Prasad B, Mishra IM. 2008. Adsorptive removal of acrylonitrile by commercial grade activated carbon: kinetics, equilibrium and thermodynamics. J Hazard Mater. 152(2):589–600. ‏ doi:10.1016/j.jhazmat.2007.07.048.
   PubMedGoogle Scholar
• Kumar D, Singh B. 2019. Algal biorefinery: an integrated approach for sustainable biodiesel production. Biomass Bioenergy. 131:105398. ‏ doi:10.1016/j.biombioe.2019.105398.
   Google Scholar
• Lee K, Lee CG. 2001. Effect of light/dark cycles on wastewater treatments by microalgae. Biotechnol Bioprocess Eng. 6(3):194–199. ‏ doi:10.1007/BF02932550.
   Google Scholar
• Li Y, Horsman M, Wu N, Lan CQ, Dubois‐Calero N. 2008. Biofuels from microalgae. Biotechnol Prog. 24(4):815–820. ‏ doi:10.1021/bp070371k.
   PubMed Web of Science ®Google Scholar
• Mahmoud AS, Ghaly AE, Brooks SL. 2007. Influence of temperature and pH on the stability and colorimetric measurement of textile dyes. Am J Biochem Biotechnol. 3(1):33–41. doi:10.3844/ajbbsp.2007.33.41.
   Google Scholar
• Martin TC, Martin JW, Alison GS. 2006. Algae need their vitamins. Minireviews, American Society for Microbiology. Eukaryotic Cell. 5(8):1175–1183.
   PubMedGoogle Scholar
• Mitter EK, Corso CR. 2013. FT-IR analysis of Acid Black dye biodegradation using Saccharomyces cerevisiae immobilized with treated sugarcane bagasse. Water Air Soil Pollut. 224(7):1–9. ‏ doi:10.1007/s11270-013-1607-0.
   Google Scholar
• Montgomery DC. 2009. Design and analysis of experiments. Hoboken (NJ): Wiley. p. 75–83.
   Google Scholar
• Oturkar CC, Nemade HN, Mulik PM, Patole MS, Hawaldar RR, Gawai KR. 2011. Mechanistic investigation of decolorization and degradation of Reactive Red 120 by Bacillus lentus BI377. Bioresour Technol. 102(2):758–764. ‏ doi:10.1016/j.biortech.2010.08.094.
   PubMedGoogle Scholar
• Ozdemir G, Pazarbasi B, Kocyigit A, Omeroglu EE, Yasa I, Karaboz I. 2008. Decolorization of Acid Black 210 by Vibrio harveyi TEMS1, a newly isolated bioluminescent bacterium from Izmir Bay, Turkey. World J Microbiol Biotechnol. 24(8):1375–1381. ‏ doi:10.1007/s11274-007-9619-9.
   Web of Science ®Google Scholar
• Perumal P, Balaji PB, Santhanam P, Ananth S, Shenbaga DA, Kumar SD. 2012. Isolation and culture of microalgae. In: Santhanam P, editor. Manual on advances in aquaculture technology. New Delhi: Springer. p. 166–181. doi:10.1007/978-81-322-2271-2_1.
   Google Scholar
• Perumal S, Thirunavukkarasu AR, Pachiappan P, editors. 2015. Advances in marine and brackishwater aquaculture. New Delhi; Heidelberg; New York; Dordrecht; London: Springer.‏
   Google Scholar
• Prasad ASA, Rao KVB. 2014. Aerobic biodegradation of azo dye Acid Black-24 by Bacillus halodurans. J Environ Biol. 35(3):549–554.
   PubMedGoogle Scholar
• Procházková G, Brányiková I, Zachleder V, Brányik T. 2014. Effect of nutrient supply status on biomass composition of eukaryotic green microalgae. J Appl Phycol. 26(3):1359–1377. ‏ doi:10.1007/s10811-013-0154-9.
   Web of Science ®Google Scholar
• Provasoli L, Carlucci A. 1974. Vitamins and growth regulators. In: Stewart WDP, editor. Algal physiology and biochemistry. Oxford: Blackwell. p. 741–787.
   Google Scholar
• Qu P, Boelte KC, Lin PC. 2012. Negative regulation of myeloid-derived suppressor cells in cancer. Immunol Invest. 41(6–7):562–580. doi:10.3109/08820139.2012.685538.
   PubMed Web of Science ®Google Scholar
• Rasdi NW, Qin JG. 2015. Effect of N: P ratio on growth and chemical composition of Nannochloropsis oculata and Tisochrysis lutea. J Appl Phycol. 27(6):2221–2230. ‏ doi:10.1007/s10811-014-0495-z.
   Web of Science ®Google Scholar
• Rathod J, Archana G. 2013. Molecular fingerprinting of bacterial communities in enriched azo dye (reactive violet 5R) decolorising native acclimatised bacterial consortia. Bioresour Technol. 142:436–444. ‏ doi:10.1016/j.biortech.2013.05.057.
   PubMedGoogle Scholar
• Robinson T, Mc-Mullan G, Marchant R, Nigam P. 2001. Remediation of dyes in textile effluent: a critical review on current treatment technologies with a proposed alternative. Bioresour Technol. 77(3):247–255. ‏ doi:10.1016/S0960-8524(00)00080-8.
   PubMed Web of Science ®Google Scholar
• Ross ME, Davis K, Mc-Coll R, Stanley MS, Day JG, Semião AJ. 2018. Nitrogen uptake by the macro-algae Cladophora coelothrix and Cladophora parriaudii: influence on growth, nitrogen preference and biochemical composition. Algal Res. 30:1–10. ‏ doi:10.1016/j.algal.2017.12.005.
   Google Scholar
• Sanz-Luque E, Ocaña‐Calahorro F, de Montaigu A, Chamizo‐Ampudia A, Llamas Á, Galván A, Fernández E. 2015. THB 1, a truncated hemoglobin, modulates nitric oxide levels and nitrate reductase activity. Plant J. 81(3):467–479. ‏doi:10.1111/tpj.12744.
   PubMedGoogle Scholar
• Sharma R, Singh GP, Sharma VK. 2011. Comparison of different media formulations on growth, morphology and chlorophyll content of green alga, Chlorella vulgaris. Int J Pharm Biol Sci. 2(2):B509–B516.
   Google Scholar
• Shedbalkar U, Dhanve R, Jadhav J. 2008. Biodegradation of triphenylmethane dye cotton blue by Penicillium ochrochloron MTCC 517. J Hazard Mater. 157(2–3):472–479. ‏ doi:10.1016/j.jhazmat.2008.01.023.
   PubMed Web of Science ®Google Scholar
• Solovchenko A, Verschoor AM, Jablonowski ND, Nedbal L. 2016. Phosphorus from wastewater to crops: an alternative path involving microalgae. Biotechnol Adv. 34(5):550–564. ‏doi:10.1016/j.biotechadv.2016.01.002.
   PubMed Web of Science ®Google Scholar
• Tam NFY, Wong YS. 2000. Effect of immobilized microalgal bead concentrations on wastewater nutrient removal. Environ Pollut. 107(1):145–151. ‏ doi:10.1016/S0269-7491(99)00118-9.
   PubMed Web of Science ®Google Scholar
• Telke AA, Joshi SM, Jadhav SU, Tamboli DP, Govindwar SP. 2010. Decolorization and detoxification of Congo red and textile industry effluent by an isolated bacterium Pseudomonas sp. SU-EBT. Biodegradation. 21(2):283–296. ‏ doi:10.1007/s10532-009-9300-0.
   PubMed Web of Science ®Google Scholar
• Turhan K, Durukan I, Ozturkcan SA, Turgut Z. 2012. Decolorization of textile basic dye in aqueous solution by ozone. Dyes Pigments. 92(3):897–901. ‏ doi:10.1016/j.dyepig.2011.07.012.
   Web of Science ®Google Scholar
• Varjani S, Upasani VN. 2019. Influence of abiotic factors, natural attenuation, bioaugmentation and nutrient supplementation on bioremediation of petroleum crude contaminated agricultural soil. J Environ Manage. 245:358–366. ‏ doi:10.1016/j.jenvman.2019.05.070.
   PubMed Web of Science ®Google Scholar
• Wang X, Sun C, Gao S, Wang L, Shuokui H. 2001. Validation of germination rate and root elongation as indicator to assess phytotoxicity with Cucumis sativus. Chemosphere. 44(8):1711–1721. ‏ doi:10.1016/S0045-6535(00)00520-8.
   PubMedGoogle Scholar
• Westman E, Muehlboeck JS, Simmons A. 2012. Combining MRI and CSF measures for classification of Alzheimer’s disease and prediction of mild cognitive impairment conversion. Neuroimage. 62(1):229–238. doi:10.1016/j.neuroimage.2012.04.056.
   PubMed Web of Science ®Google Scholar
• Xin L, Hong-Ying H, Ke G, Jia Y. 2010b. Growth and nutrient removal properties of a freshwater microalga Scenedesmus sp. LX1 under different kinds of nitrogen sources. Ecol Eng. 36(4):379–381. doi:10.1016/j.ecoleng.2009.11.003.
   Web of Science ®Google Scholar
• Xin L, Hong-Ying H, Ke G, Ying-Xue S. 2010a. Effects of different nitrogen and phosphorus concentrations on the growth, nutrient uptake, and lipid accumulation of a freshwater microalga Scenedesmus sp. Bioresour Technol. 101(14):5494–5500. ‏ doi:10.1016/j.biortech.2010.02.016.
   PubMed Web of Science ®Google Scholar
• Xu M, Guo J, Sun G. 2007. Biodegradation of textile azo dye by Shewanella decolorationis S12 under microaerophilic conditions. Appl Microbiol Biotechnol. 76(3):719–726. ‏ doi:10.1007/s00253-007-1032-7.
   PubMedGoogle Scholar
• Yew GY, Lee SY, Show PL, Tao Y, Law CL, Nguyen TTC, Chang JS. 2019. Recent advances in algae biodiesel production: from upstream cultivation to downstream processing. Bioresour Technol Rep. 7:100227. ‏ doi:10.1016/j.biteb.2019.100227.
   Google Scholar