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Integration of first and second generation bioethanol processes using edible filamentous fungus Neurospora intermedia
University of Borås, Faculty of Textiles, Engineering and Business.ORCID iD: 0000-0001-5719-7252
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Establishing a commercial, lignocellulose-based, second-generation ethanol process has received several decades of attention by both researchers and industry. However, a fully economically viable process still remains a long-term goal. The main bottleneck to this achievement is the recalcitrance of lignocellulosic feedstocks, although there are several other factors, such as the huge investment required for second-generation ethanol facilities. An intelligent alternative solution discussed in this thesis is an integrated approach using firstgeneration ethanol plants for second-generation processes. Wheat is the major feedstock for first-generation ethanol in Europe; therefore, wheat-based lignocellulose waste, such as wheat straw, bran, and whole stillage fiber (a waste stream from first-generation wheat-based ethanol plants) was the primary focus of the integration model in this thesis. Since the major share of first-generation ethanol plant economics focuses on the animal feed DDGS (Distillers’ dried gains with solubles), the integration of lignocellulose should be designed in order to maintain DDGS quality. An ethanol-producing edible filamentous fungus, Neurospora intermedia, a potential protein source in DDGS, was considered for use as the fermenting microbe. The morphological and physiological aspects of this fungus were studied in the thesis, leading to the first report of fungal pellet development.

An alternative approach of using dilute phosphoric acid to pretreat lignocellulose, as it does not negatively affect fungal growth or DDGS quality, was demonstrated in both the laboratory and on a 1m3 pilot scale. Furthermore, the process of hydrolysis of pretreated lignocelluloses and subsequent N. intermedia fermentation on lignocellulose hydrolysate was also optimized in the laboratory and scaled up to 1 m3 using an in-house pilot-scale airlift bioreactor. Fungal fermentation on acid-pretreated and enzyme-hydrolyzed wheat bran, straw and whole stillage fiber resulted in a final ethanol yield of 95%, 94% and 91% of the theoretical maximum based on the glucan content of the substrate, respectively. Integrating the first- and second-generation processes using thin stillage (a waste stream from first-generation wheat-based ethanol plants) enhanced the fungal growth on straw hydrolysate, avoiding the need for supplementing with extra nutrients.

Based on the results obtained from this thesis work, a new model for integrated first- and second-generation ethanol using edible filamentous fungi processes that also adds value to animal feed (DDGS) was developed.

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2017.
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 82
Keyword [en]
First- and second-generation bioethanol, Integration, Neurospora intermedia, Edible filamentous fungi, Wheat straw, Wheat bran, Whole stillage fiber
National Category
Natural Sciences
Identifiers
URN: urn:nbn:se:hb:diva-12436ISBN: 978-91-88269-51-5 (print)ISBN: 978-91-88269-52-2 (electronic)OAI: oai:DiVA.org:hb-12436DiVA: diva2:1128276
Available from: 2017-09-13 Created: 2017-07-24 Last updated: 2017-09-22Bibliographically approved
List of papers
1. Dilute phosphoric acid pretreatment of wheat bran for enzymatic hydrolysis and subsequent ethanol production by edible fungi Neurospora intermedia.
Open this publication in new window or tab >>Dilute phosphoric acid pretreatment of wheat bran for enzymatic hydrolysis and subsequent ethanol production by edible fungi Neurospora intermedia.
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2015 (English)In: Industrial crops and products (Print), ISSN 0926-6690, E-ISSN 1872-633X, Vol. 69, 314-323 p.Article in journal (Refereed) Published
Abstract [en]

The use of an underutilized and abundant lignocellulosic feedstock residue, wheat bran, was studied for ethanol prodn. using dil. phosphoric acid pretreatment followed by fermn. using edible fungi Neurospora intermedia. Wheat bran was subjected to dil. acid pretreatment at varying acid concns. (0.5-3.0% w/v), temp. (150-210 °C), and reaction time (5-20 min). The interaction of multiple factors showed the optimum pretreatment conditions at acid concn. of 1.75% (w/v), at 190 °C for 10 min. The max. total polysaccharide yield of 0.27 ± 0.01 g/g dry biomass loading, corresponding to 66% of the theor. max. was obsd. Subsequent fermn. with N. intermedia showed 85% of the theor. max. ethanol yield from the untreated bran glucose. The effect of the dil. acid pretreatment on the functional groups of the wheat bran cellulose was detd. with 78% redn. in the cellulose crystallinity index. The validation of the dil. phosphoric acid pretreatment in a demo plant is also reported for the first time. Enzymic hydrolysis of pretreated slurry from the demo plant showed 85% total theor. yield of polysaccharides. Compared to the untreated bran biomass, an increase of 51% was obsd. in the ethanol yield following pretreatment, with a total ethanol yield of 95% theor. max. Higher yield of ethanol is also attributed to the xylose fermenting capability of the fungi. [on SciFinder(R)]

Keyword
Dilute phosphoric acid, Edible fungi, Ethanol fermentation, Neurospora intermedia, Pretreatment, Wheat bran
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:hb:diva-88 (URN)10.1016/j.indcrop.2015.02.038 (DOI)000355365300041 ()84923361612 (Scopus ID)
Available from: 2015-12-06 Created: 2015-05-22 Last updated: 2017-09-22Bibliographically approved
2. Optimizing dilute phosphoric acid pretreatment of wheat straw in the laboratory and in a demonstration plant for ethanol and edible fungal biomass production using Neurospora intermedia.
Open this publication in new window or tab >>Optimizing dilute phosphoric acid pretreatment of wheat straw in the laboratory and in a demonstration plant for ethanol and edible fungal biomass production using Neurospora intermedia.
2016 (English)In: Journal of chemical technology and biotechnology (1986), ISSN 0268-2575, E-ISSN 1097-4660Article in journal (Refereed) Published
Abstract [en]

BACKGROUND : A method is described that uses dil. phosphoric acid for wheat straw pretreatment and subsequent ethanol and fungal biomass prodn. with the edible fungus Neurospora intermedia. Dil. phosphoric acid pretreatment of wheat straw was optimized at a lab. scale, and the results were validated in a biorefinery demonstration plant for the first time. The various conditions for the dil. acid pretreatment include such factors as phosphoric acid concns. (0.5-3.0% w/v), temp. (150-210 °C), and reaction time (5-20 min). RESULTS : The optimal pretreatment conditions were detd. as an acid concn. of 1.75% (w/v) at a temp. of 190 °C for 15 min, based on the max. enzymic digestibility with the min. inhibitor release. The efficiency of enzymic polysaccharide hydrolysis was 36% for untreated straw and 86% for straw pretreated with dil. phosphoric acid. Scale up of the pretreatment at a biorefinery demonstration plant improved the process, with the subsequent efficiency of polysaccharide hydrolysis being 95% of the theor. max. Ethanol fermn. of enzymically hydrolyzed wheat straw using N. intermedia showed an improvement in the ethanol yield from 29% (with untreated straw) to 94% (with dil. phosphoric acid pretreated straw) of the theor. max. CONCLUSION : This study opens up an alternative strategy for the efficient use of wheat straw for the prodn. of ethanol and edible fungal biomass in existing wheat-to-ethanol plants.

Keyword
Dilute phosphoric acid, Ethanol, Fermentation, Filamentous fungi, Optimization, Pretreatment
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:hb:diva-11393 (URN)10.1002/jctb.5119 (DOI)84997724781 (Scopus ID)
Note

CAPLUS AN 2016:1751717(Journal)

Available from: 2016-12-14 Created: 2016-12-14 Last updated: 2017-09-22Bibliographically approved
3. Integrated Process for Ethanol, Biogas, and Edible Filamentous Fungi-Based Animal Feed Production from Dilute Phosphoric Acid-Pretreated Wheat Straw
Open this publication in new window or tab >>Integrated Process for Ethanol, Biogas, and Edible Filamentous Fungi-Based Animal Feed Production from Dilute Phosphoric Acid-Pretreated Wheat Straw
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2017 (English)In: Applied Biochemistry and Biotechnology, ISSN 0273-2289, E-ISSN 1559-0291, 1-15 p.Article in journal (Refereed) Published
Abstract [en]

Integration of wheat straw for a biorefinery-based energy generation process by producing ethanol and biogas together with the production of high-protein fungal biomass (suitable for feed application) was the main focus of the present study. An edible ascomycete fungal strain Neurospora intermedia was used for the ethanol fermentation and subsequent biomass production from dilute phosphoric acid (0.7 to 1.2% w/v) pretreated wheat straw. At optimum pretreatment conditions, an ethanol yield of 84 to 90% of the theoretical maximum, based on glucan content of substrate straw, was observed from fungal fermentation post the enzymatic hydrolysis process. The biogas production from the pretreated straw slurry showed an improved methane yield potential up to 162% increase, as compared to that of the untreated straw. Additional biogas production, using the syrup, a waste stream obtained post the ethanol fermentation, resulted in a combined total energy output of 15.8 MJ/kg wheat straw. Moreover, using thin stillage (a waste stream from the first-generation wheat-based ethanol process) as a co-substrate to the biogas process resulted in an additional increase by about 14 to 27% in the total energy output as compared to using only wheat straw-based substrates. .[on SciFinder (R)]

Keyword
bioethanol, biogas, dilute acid pretreatment, filamentous fungi, integration, n. intermedia, wheat straw
National Category
Industrial Biotechnology
Identifiers
urn:nbn:se:hb:diva-12539 (URN)10.1007/s12010-017-2525-1 (DOI)85020404803 (Scopus ID)
Note

Copyright (C) 2017 U.S. National Library of Medicine.; MEDLINE AN 2018665916(Journal; Article; (JOURNAL ARTICLE))

Available from: 2017-08-27 Created: 2017-08-27 Last updated: 2017-09-22Bibliographically approved
4. Mycelial pellet formation by edible ascomycete filamentous fungi, Neurospora intermedia
Open this publication in new window or tab >>Mycelial pellet formation by edible ascomycete filamentous fungi, Neurospora intermedia
2016 (English)In: AMB Express, ISSN 2191-0855, E-ISSN 2191-0855, Vol. 6, no 31, 10.1186/s13568-016-0203-2Article in journal (Refereed) Published
Abstract [en]

Pellet formation of filamentous fungi in submerged culture is an imperative topic of fermentation research. In this study, we report for the first time the growth of filamentous ascomycete fungus,Neurospora intermedia in its mycelial pellet form. In submerged culture, the growth morphology of the fungus was successfully manipulated into growing as pellets by modifying various cultivation conditions. Factors such as pH (2.0–10.0), agitation rate (100–150 rpm), carbon source (glucose, arabinose, sucrose, and galactose), the presence of additive agents (glycerol and calcium chloride) and trace metals were investigated for their effect on the pellet formation. Of the various factors screened, uniform pellets were formed only at pH range 3.0–4.0, signifying it as the most influential factor for N. intermedia pellet formation. The average pellet size ranged from 2.38 ± 0.12 to 2.86 ± 0.38 mm. The pellet formation remained unaffected by the inoculum type used and its size showed an inverse correlation with the agitation rate of the culture. Efficient glucose utilization was observed with fungal pellets, as opposed to the freely suspended mycelium, proving its viability for fast- fermentation processes. Scale up of the pelletization process was also carried out in bench-scale airlift and bubble column reactors (4.5 L).

Place, publisher, year, edition, pages
Springer Berlin/Heidelberg, 2016
Keyword
Neurospora intermedia; Ascomycete; Filamentous fungi; Edible fungi; Pellet
National Category
Bioprocess Technology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-10462 (URN)10.1186/s13568-016-0203-2 (DOI)
Funder
Swedish Energy AgencySwedish Research Council Formas
Available from: 2016-08-05 Created: 2016-08-05 Last updated: 2017-09-22Bibliographically approved

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