Enhancement of biomass and lipid production of microalgae in mixed populations in waste water : suitability to wastewater purification and biomass and lipid
Katyal, Neha (2013)
Katyal, Neha
Lahden ammattikorkeakoulu
2013
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Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2014112416384
https://urn.fi/URN:NBN:fi:amk-2014112416384
Tiivistelmä
ALGIND which is “Algae Energy Business Opportunities in India” aims to form a realistic picture for enhanced business opportunities in algal biofuel markets in India. This project aims at integrating biodiesel production with waste and wastewater treatment in processes that flexibly can be tailored and linked to local facilities and offer a way to reduce operational costs related to algal cultivation. This project is realized in co-operation between University of Helsinki (UHEL), VTT, Lahti University of applied sciences (LUAS), Aalto University and international partners are: The energy and Resources institute (TERI), G.B. Pant Univ. of agriculture and technology (GBPUAT) and Manav Rachna International University (MRIU).
This Master’s thesis assesses the potential of microalgae for waste waterpurification and biodiesel production in single and mixed populations. The wastewater used in these experiments was pressed from mixture of new municipal organic waste and partly composted garden waste. The species that have been chosen for growth during the experiments are Euglena gracilis, Selenastrum sp. and Chlorella pyrenoidosa and their various combinations. The experiments have been carried out at lab-scale and photobioreactors. Samples were taken on a regular interval (3 times a week) for determination of growth (DW), growth rate and nutrient consumption. Microscopy was used for calculation of cell concentrations (cells mL-1) in the end of the cultivation. In the laboratory scale experiments, individual population of C.pyrenoidosa had highest and Selenastrum lowest biomass concentration in the end of cultivation (1.2±0.3 and 0.7±0.1 gL-1 DW). Biomass concentration of E.gracilis culture reached 1.0 ±0.04 gL-1 DW. Development of biomass was used for determination of growth rate in pure and mixed cultures. The growth rates were with C.pyrenoidosa (0.11d-1), Selenastrum (0.10 d-1) and E.gracilis (0.14 d-1) in laboratory cultures. The combination of C.Pyrenoidosa with E.gracilis and C.pyrenoidosa with Selenastrum showed biomass concentrations 0.7±0.1 gL-1 DW and 0.8±0.1 gL-1 DW. In the laboratory scale cultivation, the growth rates were similar for mixed populations of C.pyrenoidosa and E.gracilis and Selenastrum and E.gracilis at 0.13 d-1. The population of C.pyrenoidosa and Selenastrum showed a growth rate of 0.16 d-1
and all the three strains together showed biomass yield of 1.0±0.1 gL-1 DW and growth rate of 0.2 d-1. In individual populations, the cell concentrations of C.pyrenoidosa have been the maximum as compared to all other cultures (8.68E+06 cells mL-1 )E.gracilis and Selenastrum a combination show survival of both the species but cell concentration of Selenastrum strain was lower (2.75E+05cells mL-1) than when it was cultured alone (2.29E+06 cells mL-1). Also, therewas presence of C.pyrenoidosa and E.gracilis together. Thus, E.gracilis individually and in combinations with Selenastrum and C.pyrenoidosa was selected for growth in reactors. In photobioreactors mixed cultures, E.gracilis survived in existence of other species better than any other species. In the end of the cultivation E.gracilis was the only strain which was observed under microscope but however there were differences in the growth rates and biomass yields between cultures. The growth rates of the cultures in photobioreactor experiments were: E.gracilis and C.pyrenoidosa 0.3 d-1, E.gracilis and Selenastrum 0.46 d-1 and E.gracilis in in pure culture 0.37 d-1. The combination of E.gracilis and Selenastrum showed biomass 0.72±0.1 gL-1 DW in the end of cultivation which was slightly lower than biomass of single population of E.gracilis which showed highest biomass (0.8±0.1 gL-1). Mixed population of C.pyrenoidosa reached the biomass The cell concentration of E.gracilis in individual population and with presence of Selenastrum was found to be similar (1.21E+06 cells mL-1). The cell concentration of E.gracilis was minor (8.48E+05 cells mL-1) when it grew in combination with C.pyrenoidosa in reactors. Ammonium removal from the wastewaters in photobioreactor was most efficient. The ammonium removal was attained highest by the combination of Selenastrum and E.gracilis (99.18%) and E.gracilis alone followed closely by combination of E.gracilis and C.pyrenoidosa (93%). The nitrate removal was seen maximum by E.gracilis and C.pyrenoidosa (41.6%) followed by E.gracilis combination with Selenastrum (30.56%) and individual population (22.4%). The phosphate removal was, however, seen maximum by combination of E.gracilis (78.4%) followed by E.gracilis and C.pyrenoidosa (76.2%) and least by E.gracilis and Selenastrum(54.3%).
Solvent extraction (Chloroform and methanol) was used for extraction of lipids. After methylation fatty acid methyl esters (FAMEs) were analysed with GCMS. Total lipid content was determined gravimetrically and total fatty acid content was expressed as sum of individual fatty acids (FA). The total lipid and FA contents were determined during the last four days of cultivation in the reactors. The content of polyunsaturated fatty acids (PUFAs), however varies in the cultures. They show the highest content in E.gracilis and Selenastrum (56.68±1.68% DW) and comparatively less in case of E.gracilis (51.47±6.06% DW) and E.gracilis and C.pyrenoidosa (51.93±4.80% DW). Some PUFAs have established health benefits but are not desirable in biodiesel raw material. The total FA content in E.gracilis population was maximal on the last day of cultivation (8.32±0.73 % DW) which is nearly double from day 1 (4.32±0.30% DW). E.gracilis and Selenastrum showed the highest FA content (12.14±2.27%DW) in the end of the cultivation and total FA content in mixed culture of E.gracilis and C.pyrenoidosa was 6.17±0.71%DW in the last day. The monounsaturated FA content was maximal in the culture of E.gracilis and Selenastrum (20.85±1.02%DW). The saturated FA content is seen maximally in the culture of E.gracilis and C.pyrenoidosa (44.97±0.34% DW). Results showed that biomass yield in the mixed cultures was mainly lower than pure cultures but there was enhancement in lipid production when E.gracilis and Selenastrum were cultured together. However, there are still concerns about these FAs since saturated FA chains are problematic for cold flow and polyunsaturated FA chains are problematic for oxidative stability (28). However results indicate that cultivation in mixed populations can reach higher lipid production but fatty acid profile of E.gracilis is not optimal for biodiesel
This Master’s thesis assesses the potential of microalgae for waste waterpurification and biodiesel production in single and mixed populations. The wastewater used in these experiments was pressed from mixture of new municipal organic waste and partly composted garden waste. The species that have been chosen for growth during the experiments are Euglena gracilis, Selenastrum sp. and Chlorella pyrenoidosa and their various combinations. The experiments have been carried out at lab-scale and photobioreactors. Samples were taken on a regular interval (3 times a week) for determination of growth (DW), growth rate and nutrient consumption. Microscopy was used for calculation of cell concentrations (cells mL-1) in the end of the cultivation. In the laboratory scale experiments, individual population of C.pyrenoidosa had highest and Selenastrum lowest biomass concentration in the end of cultivation (1.2±0.3 and 0.7±0.1 gL-1 DW). Biomass concentration of E.gracilis culture reached 1.0 ±0.04 gL-1 DW. Development of biomass was used for determination of growth rate in pure and mixed cultures. The growth rates were with C.pyrenoidosa (0.11d-1), Selenastrum (0.10 d-1) and E.gracilis (0.14 d-1) in laboratory cultures. The combination of C.Pyrenoidosa with E.gracilis and C.pyrenoidosa with Selenastrum showed biomass concentrations 0.7±0.1 gL-1 DW and 0.8±0.1 gL-1 DW. In the laboratory scale cultivation, the growth rates were similar for mixed populations of C.pyrenoidosa and E.gracilis and Selenastrum and E.gracilis at 0.13 d-1. The population of C.pyrenoidosa and Selenastrum showed a growth rate of 0.16 d-1
and all the three strains together showed biomass yield of 1.0±0.1 gL-1 DW and growth rate of 0.2 d-1. In individual populations, the cell concentrations of C.pyrenoidosa have been the maximum as compared to all other cultures (8.68E+06 cells mL-1 )E.gracilis and Selenastrum a combination show survival of both the species but cell concentration of Selenastrum strain was lower (2.75E+05cells mL-1) than when it was cultured alone (2.29E+06 cells mL-1). Also, therewas presence of C.pyrenoidosa and E.gracilis together. Thus, E.gracilis individually and in combinations with Selenastrum and C.pyrenoidosa was selected for growth in reactors. In photobioreactors mixed cultures, E.gracilis survived in existence of other species better than any other species. In the end of the cultivation E.gracilis was the only strain which was observed under microscope but however there were differences in the growth rates and biomass yields between cultures. The growth rates of the cultures in photobioreactor experiments were: E.gracilis and C.pyrenoidosa 0.3 d-1, E.gracilis and Selenastrum 0.46 d-1 and E.gracilis in in pure culture 0.37 d-1. The combination of E.gracilis and Selenastrum showed biomass 0.72±0.1 gL-1 DW in the end of cultivation which was slightly lower than biomass of single population of E.gracilis which showed highest biomass (0.8±0.1 gL-1). Mixed population of C.pyrenoidosa reached the biomass The cell concentration of E.gracilis in individual population and with presence of Selenastrum was found to be similar (1.21E+06 cells mL-1). The cell concentration of E.gracilis was minor (8.48E+05 cells mL-1) when it grew in combination with C.pyrenoidosa in reactors. Ammonium removal from the wastewaters in photobioreactor was most efficient. The ammonium removal was attained highest by the combination of Selenastrum and E.gracilis (99.18%) and E.gracilis alone followed closely by combination of E.gracilis and C.pyrenoidosa (93%). The nitrate removal was seen maximum by E.gracilis and C.pyrenoidosa (41.6%) followed by E.gracilis combination with Selenastrum (30.56%) and individual population (22.4%). The phosphate removal was, however, seen maximum by combination of E.gracilis (78.4%) followed by E.gracilis and C.pyrenoidosa (76.2%) and least by E.gracilis and Selenastrum(54.3%).
Solvent extraction (Chloroform and methanol) was used for extraction of lipids. After methylation fatty acid methyl esters (FAMEs) were analysed with GCMS. Total lipid content was determined gravimetrically and total fatty acid content was expressed as sum of individual fatty acids (FA). The total lipid and FA contents were determined during the last four days of cultivation in the reactors. The content of polyunsaturated fatty acids (PUFAs), however varies in the cultures. They show the highest content in E.gracilis and Selenastrum (56.68±1.68% DW) and comparatively less in case of E.gracilis (51.47±6.06% DW) and E.gracilis and C.pyrenoidosa (51.93±4.80% DW). Some PUFAs have established health benefits but are not desirable in biodiesel raw material. The total FA content in E.gracilis population was maximal on the last day of cultivation (8.32±0.73 % DW) which is nearly double from day 1 (4.32±0.30% DW). E.gracilis and Selenastrum showed the highest FA content (12.14±2.27%DW) in the end of the cultivation and total FA content in mixed culture of E.gracilis and C.pyrenoidosa was 6.17±0.71%DW in the last day. The monounsaturated FA content was maximal in the culture of E.gracilis and Selenastrum (20.85±1.02%DW). The saturated FA content is seen maximally in the culture of E.gracilis and C.pyrenoidosa (44.97±0.34% DW). Results showed that biomass yield in the mixed cultures was mainly lower than pure cultures but there was enhancement in lipid production when E.gracilis and Selenastrum were cultured together. However, there are still concerns about these FAs since saturated FA chains are problematic for cold flow and polyunsaturated FA chains are problematic for oxidative stability (28). However results indicate that cultivation in mixed populations can reach higher lipid production but fatty acid profile of E.gracilis is not optimal for biodiesel