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Microbial community diversity of organically rich cassava sago factory waste waters and their ability to use nitrate and N2O added as external N-sources for enhancing biomethanation and the purification efficiency

Paper ID Volume ID Publish Year Pages File Format Full-Text
23317 43431 2013 10 PDF Available
Title
Microbial community diversity of organically rich cassava sago factory waste waters and their ability to use nitrate and N2O added as external N-sources for enhancing biomethanation and the purification efficiency
Abstract

Water shortage necessitated South Indian sago factory owners, extracting starch out of cassava tubers, to install biogas plants where a starch utilizing microbial community multiplies and reduces the biological oxygen demand (BOD) of the waste waters by presently about 30%. The purification efficiency of sago factory waste waters, rich in solid particles and having wide C/N ratios, around 250, through unstirred biogas plants needs to be improved. Our approach was to apply instead of animal slurry nitrate (NO3−) and nitrous oxide (N2O) as external N-sources anticipating a better N-distribution in the unstirred biogas plants.Estimated cell numbers, bacterial community changes, on the basis of 16S rRNA gene clone libraries and changing CO2-, CH4-, N2O releases due to the presence of nitrate or N2O suggest that acid tolerant Lactobacillus spp. dominate the biogas plant inflows (pH 3.5). They were very less or not found in the outflows (pH 7.3). Assumingly, the phyla Bacteroidetes (Prevotella spp.), Proteobacteria (Rhizobium spp., Defluvibacter sp.), Firmicutes (Megasphaera spp., Dialister spp., Clostridium spp.) and Synergistetes (Thermanaerovibrio spp.), not-detectable in the biogas plant inflows, replaced them. Anaerobes, about 400 cells ml−1 in the inflows, increased to about 106 cells ml−1 in the outflows. The methane formation, as confirmed by the incubation experiments, suggests that methanogens must have been present among the anaerobes. In the biogas plant in- and outflows also about 300 cells ml−1 denitrifying bacteria and up to 104 cfu fungi were found.Despite the low number of denitrifying bacteria nitrate added to the biogas plant in- and outflows was widely consumed and added N2O decreased considerably. Thus, wide C/N ratios substrates like sago factory waste waters keep the N2O emissions low by using N2O either as electron acceptor or by incorporating it into the growing biomass what needs to be confirmed. The biogas plant inflow samples have emitted tentatively more CO2 and the outflow samples released more CH4.

► Indian chemically and microbiologically characterized sago factory waste waters have extremely wide CN ratios. ► BOD degradation in biogas plants is N-limited and bacterial shifting is observed and reported. ► Larger sized microbes (protozoa, oomycetes, chytrids) may play a role in carbohydrate conversion. ► Biogas plants samples of 3 differently sized sago factories were enriched with nitrate or N2O. ► Nitrate and N2O are rapidly incorporated or reduced to N2 but negatively affect the CH4-release.

Keywords
Starch rich waste waters; Wide C/N ratio; Biogas plant purification; External biogas plant purification; External N-source N2O; Microbial diversity changes
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Microbial community diversity of organically rich cassava sago factory waste waters and their ability to use nitrate and N2O added as external N-sources for enhancing biomethanation and the purification efficiency
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Publisher
Database: Elsevier - ScienceDirect
Journal: Journal of Biotechnology - Volume 164, Issue 2, March 2013, Pages 266–275
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us