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Subject: Microbiology × Author: Dar, Rouf Ahmad × End date: 2019 × Start date: 2017 × Thesis Type: Ph.D ×
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    ThesisItemOpen Access
    Bioprospects of microalgal isolates from water logged area of Punjab for biogas production
    (Punjab Agricultural University, Ludhiana, 2017) Dar, Rouf Ahmad; Phutela, Urmila Gupta
    The present study was aimed at isolation, identification, screening and characterization of microalgae from the waterlogged area of south-west Punjab, India. Optimization of cultural conditions of potential microalgal strains, their biogas production potential and anaerobic co-digestion studies were also conducted. Nineteen microalgal cultures (BGLR1-BGLR19) were isolated and were screened using different culture media for their growth kinetics. Isolate BGLR6 followed by BGLR5 showed the highest growth and biomass production in Algae culture medium and BG-11 medium respectively. These isolates upon molecular identification were found to be Asterarcys quadricellulare BGLR5 (MF661929) and Spirulina subsalsa BGLR6 (MF191711). The cultivation conditions for the enhanced production of biomass and other functional components (chlorophyll, carbohydrate, lipid and protein) of BGLR5 and BGLR6 were first screened by Plackett–Burman design and then the significant factors were optimized by Central Composite design (CCD). The optimal cultural conditions for BGLR5 and BGLR6 as per the model were pH of 9.92 & 11.5; temperature of 21.84 & 20°C; light intensity of 80.99 & 81 μmol m-2 s-1; growth period of 25 days (both); 15.00 mM NH4Cl/ CaCl2; 12.28 & 5.00 mM NaNO3 and 7.09 & 2.00 mM K2HPO4 respectively. Under these conditions, the response variables generated a desirability index of 84.10 and 94.91% for BGLR5 and BGLR6 respectively. A 0.42 and 1.60-fold increase in dry cell biomass yield was achieved in BGLR5 and BGLR6, compared to the basal condition (0.8858 and 1.0890 g biomass L-1) respectively. The biogas potential of the microalgal biomass under controlled temperature (35 ± 2°C) conditions revealed that in case of BGLR5, the highest biogas yield (51.712 Lkg-1algal biomass) was obtained in the hydrothermally (100°C 30min) pretreated biomass whilst in BGLR6, the highest biogas yield (42.73 Lkg-1algal biomass) was obtained in enzymatically (10% 24hr) pretreated biomass. Further, co-digestion of 50% paddy straw and 50% BGLR5 biomass (replacement of paddy straw by equal amount of microalgal biomass) produced 168.32 L biogas kg-1 feedstock with the ultimate biogas yield potential of 361.81 mLg-1 VS, reduced lag phase (λ:2.81 d) and increased rate of biogas production (Rm: 8.19 mLg-1d -1) which was higher not only in comparison to the anaerobic digestion of paddy straw and algal biomass individually but also to that of co-digestion of BGLR6 biomass with paddy straw. Likewise, 50 and 100% supplementation of BGLR5 biomass led to enhanced biogas production. Utilization of algal biomass cultivated in the open pond for co-digestion study with paddy straw in field scale digesters resulted in an increase of 17.27% biogas compared to control. The enhancement of methane content from 46.4% (control) to 66.5% (digester containing algal biomass) was also achieved. Hence, the present study signifies that the Asterarcys quadricellulare BGLR5 and Spirulina subsalsa BGLR6 biomass could be utilized as a cofeedstock with paddy straw for biogas production.