Enrichment of Emphasis Type="Italic"Parachlorell

Authors: Agata Piasecka Izabela Krzemińska Jerzy Tys

Publish Date: 2017/02/13

Volume: 29, Issue: 4, Pages: 1735-1743

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Abstract

The aim of this study was to determine the suitability of beet molasses an agroindustrial byproduct as an alternative culture medium component for photoheterotrophic and mixotrophic cultivation of Parachlorella kessleri Application of beet molasses improved microalgal cell growth and modified the biochemical composition of P kessleri biomass During the addition of molasses to culture media with simultaneous aeration the maximum biomass productivity oil and protein productivity and calorific value were 042 g L−1 day−1 11256 and 24495 mg L−1 day−1 and 221 MJ kg−1 respectively Under these conditions the total content of polyunsaturated C16C18 fatty acids decreased which was suitable for application in biodiesel Besides oils and carbohydrates P kessleri had an ability to synthesize significant amounts of proteins especially during molasses utilization This provides a possibility of a wide range of nonfuel applications of P kessleri biomassAlgal biofuels have been considered as one of the most promising options to provide global energy needs However algal technology has yet to overcome the cost of production and processing technology It is important to reduce the cost of microalgal biomass production Under mixotrophic conditions based on wastewater media microalgae may bring flexibility to improve production economics while generating valuable products Lowrey et al 2015 Organic carbon sources like glucose or acetate are usually costly and are responsible for most of the medium costs A cheap industrial byproduct such as molasses could be used as a lowcost medium supplement to reduce the costs of microalgal biomass production In addition the technology of microalgal culturing is becoming greener Yan et al 2011 Mitra et al 2012 Molasses is a byproduct in a sugar industry consisting of approximately 50 of total sugars predominantly sucrose but containing significant amounts of reducing sugars—glucose and fructose and other carbohydrates Polish Standard PNR64772 PNISO 64962002 The nonsugar content includes many metal ions such as calcium magnesium potassium sodium iron and cooper Liu et al 2012 It is also a source of nitrogen Until now molasses has been reported as a carbon source for the production of Botryococcus braunii Scenedesmus obliquus Auxenochlorella protothecoides Chlorella protothecoides Chromochloris zofingiensis Chlorella zofingiensis and Chlorella minutissima biomass for astaxanthin or biodiesel production Yan et al 2011 Liu et al 2012 ElSheekh et al 2013 Gautam et al 2013 Liu et al 2013 Yeesang and Cheirsilp 2014Parachlorella kessleri is a green alga with cells capable of utilizing organic carbon sources such as glucose Wang et al 2012 ethanol and glycerol Wang et al 2013 This makes P kessleri a great candidate for photoheterotrophic and mixotrophic cultivation that offers great potential in the production of microalgal renewable biomass for biodiesel production and for different applications To our knowledge there is no reported study investigating the use of molasses for P kessleri culturingMicroalgal biomass production for biodiesel also could be combined with production of other valuable compounds which may contribute to a direct reduction of costs Combined production of oil and other bioactive products provides environmental and economic sustainability of microalgal technology Bellou et al 2014 The cited authors have reviewed the existing literature and presented polysaccharides proteins and pigments as highvalue metabolites in combining oil production for commercial applications especially animal feed aquaculture fish feed and pharmaceutical and nutraceutical productsThe objective of the present study was to investigate the influence of the addition of molasses to the culture medium on P kessleri growth biomass composition and calorific value Additionally the work was intended to determine the potential of the agroindustrial byproduct as an alternative culture medium component that guarantees production of more than one compound from P kessleri biomassThe initial Parachlorella kessleri strain was obtained from the Culture Collection of Autotrophic Organisms CCALA at the Charles University in Prague Kessler medium was used as a basic medium The Kessler medium Kessler and Czygan 1970 was prepared on distilled water and was composed of per litre 081 g KNO3 047 g NaCl 047 g NaH2PO4·2H2O 036 g Na2HPO4·12H2O 025 g MgSO4·7H2O 0014 g CaCl2·2H2O 0006 g FeSO4·7H2O 00005 g MnCl2·4H2O 00005 g H3BO3 00002 g ZnSO4·7H2O 000002 g NH46Mo7O24·4H2O and 0008 g EDTA In order to prepare the preculture the liquid Kessler medium was inoculated from a 2 agar plate Preculture was incubated in 25 ± 1 °C for 10 days under continuous illumination 80 μmol photons m−2 s−1 in 50mL Erlenmeyer flasks and agitated at 100 rpm The preculture was used as an inoculum in the experimentThe effect of the application of beet molasses in culture medium on the growth and biochemical composition of P kessleri biomass was studied The experimental variants included autotrophic cultivation of KA photoheterotrophic cultivation of KM and mixotrophic cultivation of KMA The control culture/airlimited autotrophic cultivation K was prepared by inoculating fresh Kessler medium This control culture for P kessleri cultivation was not supplied with any carbon source For autotrophic conditions the Kessler medium was constantly aerated Waste beet molasses was obtained from a local sugar refinery Lublin Province Poland To prepare photoheterotrophic and mixotrophic conditions 10 g L−1 molasses was rinsed with demineralised water twice before adding to the Kessler medium and sterilizedCultivation was carried out in four variants marked sequentially as K control KA Kessler medium with aeration KM Kessler medium with molasses and KMA Kessler medium with molasses and aeration The P kessleri cells were cultivated in 3L photobioreactors BIOSTAT PBR 2S Sartorius Stedim Biotech The cultures were continuously illuminated by fluorescent lamps The light intensity was 80 μmol photons m−2 s−1 at 25 ± 1 °C The KA and KMA cultures were continuously aerated with sterile air at 12 L h−1 airflow

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