Bioprospects of microalgal isolates from water logged area of Punjab for biogas production
Loading...
Date
2017
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Punjab Agricultural University, Ludhiana
Abstract
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.
Description
Keywords
null