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Spent sulphite liquor for cultivation of an edible Rhizopus sp.
University of Borås, School of Engineering.
University of Borås, School of Engineering.
University of Borås, School of Engineering.
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2012 (English)In: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 7, no 1, 173-188 p.Article in journal (Refereed) Published
Abstract [en]

Spent sulphite liquor, the major byproduct from the sulphite pulp production process, was diluted to 50% and used for production of an edible zygomycete Rhizopus sp. The focus was on production, yield, and composition of the fungal biomass composition. The fungus grew well at 20 to 40°C, but 32°C was found to be preferable compared to 20 and 40°C in terms of biomass production and yield (maximum of 0.16 g/g sugars), protein content (0.50-0.60 g/g), alkali-insoluble material (AIM) (ca 0.15 g/g), and glucosamine content (up to 0.30 g/g of AIM). During cultivation in a pilot airlift bioreactor, the yield increased as aeration was raised from 0.15 to 1.0 vvm, indicating a high demand for oxygen. After cultivation at 1.0 vvm for 84 h, high yield and production of biomass (up to 0.34 g/g sugars), protein (0.30-0.50 g/g), lipids (0.02-0.07 g/g), AIM (0.16-0.28 g/g), and glucosamine (0.22-0.32 g/g AIM) were obtained. The fungal biomass produced from spent sulphite liquor is presently being tested as a replacement for fishmeal in feed for fish aquaculture and seems to be a potential source of nutrients and for production of glucosamine.

Place, publisher, year, edition, pages
North Carolina State University: College of Natural Resources , 2012. Vol. 7, no 1, 173-188 p.
Keyword [en]
spent sulphite liquor, airlift bioreactor, zygomycetes, rhizopus, chitosan, lipids, protein
Keyword [sv]
Energi och material
National Category
Engineering and Technology
Research subject
Resource Recovery
Identifiers
URN: urn:nbn:se:hb:diva-3194ISI: 000304041200016Local ID: 2320/9527OAI: oai:DiVA.org:hb-3194DiVA: diva2:871291
Available from: 2015-11-13 Created: 2015-11-13 Last updated: 2016-09-28Bibliographically approved
In thesis
1. Integration of filamentous fungi in ethanol dry-mill biorefinery
Open this publication in new window or tab >>Integration of filamentous fungi in ethanol dry-mill biorefinery
2015 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The industrial production of bioethanol as a replacement to gasoline is well-established worldwide, using starch- or sugar-rich substrates. Additionally, the bioethanol plants produce animal feeds derived from fermentation leftovers. The biorefinery character of bioethanol plants can be enhanced via process diversification. This entails the production of more value-added products, which can be accomplished by including edible filamentous fungi as the second biocatalysts while taking advantage of the available equipment for cost-effective inclusion. The process diversification can be achieved either via valorisation of the process leftovers or via inclusion of other residual substrates.

 

In dry-mill biorefineries, baker’s yeast is unable to consume residual pentose sugars and other more complex substrates in the process leftovers so called whole stillage and thin stillage. Edible ascomycetes and zygomycetes fungi can be used to accomplish yeast and consume those residual substrates in stillage as well as from external substrates of lignocellulosic origin, e.g. spent sulphite liquor and wheat straw. The conversion of these substrates to ethanol, and biomass rich in protein, lipids, respective essential amino acids and fatty acids as well as chitosan was investigated in this thesis.

 

Among the filamentous fungi studied, Neurospora intermedia was the best ethanol producer from thin stillage. Process developments included primary shake-flasks experiments, followed by pilot scale-up using 26 L, 2.3 m3 and 80 m3 bioreactors. The 26 L bioreactor, as a bubble column led to similar performance as an airlift bioreactor, and also a continuous mode could be successfully used instead of a batch process. By using a dilution rate of 0.1 h-1, around 5 g/L of ethanol and 4 g/L of biomass rich in protein, lipids, amino acids and fatty acids essential to humans were obtained. The inclusion of the process can potentially lead to a spent medium lower in solids and viscosity which may facilitate the energy-intensive evaporation and drying steps as well as the water recycling back to the process. By applying a two-stage cultivation with whole stillage, up to 7.6 g/L of ethanol could be produced using 1 FPU cellulase/g suspended solids and 5.8 g/L of biomass containing 42% (w/w) crude protein. In the first stage (ethanol production), N. intermedia was used, while Aspergillus oryzae was the biocatalyst in the second stage for further biomass production. Both strains were able to degrade complex substrates both in liquid and solid fraction of whole stillage. The extrinsic substrates included spent sulphite liquor and pretreated wheat straw slurry. When the former was used, up to around 7 g/L of Rhizopus sp. could be obtained in a 26 L airlift bioreactor. The biomass was rich in protein and lipids (30–50% and 2–7% on a dry weight basis, respectively). The monomers of the latter were continuously filtered for production of biomass under simultaneous saccharification fermentation and filtration. Biomass yields of up to 0.34 g/g of consumed monomeric sugars and acetic acid were obtained.

 

The inclusion of the process for valorisation of thin stillage can potentially lead to the production of 11,000 m3 ethanol and 6,300 tonnes of biomass at a typical facility producing 200,000 m3 ethanol/year.

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2015. 96 p.
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 73
Keyword
airlift bioreactors, ascomycetes, biomass, bubble column, ethanol, feed, Neurospora intermedia, thin stillage, zygomycetes
National Category
Environmental Biotechnology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-674 (URN)978-91-87525-77-3 (ISBN)978-91-87525-78-0 (ISBN)
Public defence
2015-11-13, E310, Allégatan, Borås, 10:00 (English)
Available from: 2015-10-20 Created: 2015-08-27 Last updated: 2015-12-18Bibliographically approved

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http://ojs.cnr.ncsu.edu/index.php/BioRes/article/view/BioRes_07_1_0173_Ferreira_LNLET_Spent_Sulphite_Liq_Edible_Rhizopus

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