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From stale bread and brewers spent grain to a new food source using edible filamentous fungi
University of Borås, Faculty of Textiles, Engineering and Business.ORCID iD: 0000-0002-0923-1097
Food and Nutrition Science, Biology and Biological Engineering, Chalmers University of Technology , Gothenburg, Sweden.
Food and Nutrition Science, Biology and Biological Engineering, Chalmers University of Technology , Gothenburg, Sweden.
Food and Nutrition Science, Biology and Biological Engineering, Chalmers University of Technology , Gothenburg, Sweden.
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2020 (English)In: Bioengineered, ISSN 2165-5979, E-ISSN 2165-5987, Vol. 11, no 1, p. 582-598Article in journal (Refereed) Published
Sustainable development
According to the author(s), the content of this publication falls within the area of sustainable development.
Abstract [en]

By-products from the food sector with a high load of organic matter present both a waste-handling problem related to expenses and to the environment, yet also an opportunity. This study aims to increase the value of stale bread and brewers spent grain (BSG) by re-introducing these residues to the food production chain by converting them to new protein-enriched products using the edible filamentous fungi Neurospora intermedia and Rhizopusoryzae. After 6 days of solid state fermentation (at 35°C, with a95% relative humidity and moisture content of 40% in the substrate) on stale bread, a nutrient-rich fungal-fermented product was produced. The total protein content, as analyzed by total amino acids, increased from 16.5% in stale sourdough bread to 21.1% (on dry weight basis) in the final product with an improved relative ratio of essential amino acids. An increase in dietary fiber, minerals (Cu, Fe, Zn) and vitamin E, as well as an addition of vitamin D2 (0.89 µg/g dry weight sample) was obtained compared with untreated stale bread. Furthermore, addition of BSG to the sourdough bread with the aim to improve textural changes after fermentation showed promising outcomes. Cultivation of N. intermedia or R. oryzae on stale sourdough bread mixed with 6.5% or 11.8% BSG, respectively, resulted in fungal-fermented products with similar textural properties to a commercial soybean burger. Bioconversion of stale bread and BSG by fungal solid state fermentation to produce a nutrient-enriched food product was confirmed to be a successful way to minimize food waste and protein shortage. © 2020, © 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

Place, publisher, year, edition, pages
Taylor and Francis Inc. , 2020. Vol. 11, no 1, p. 582-598
Keywords [en]
Neurospora intermedia, stale bread, brewers spent grain, edible filamentous fungi, solid state fermentation
National Category
Industrial Biotechnology
Research subject
Resource Recovery
Identifiers
URN: urn:nbn:se:hb:diva-23349DOI: 10.1080/21655979.2020.1768694ISI: 000619926100001Scopus ID: 2-s2.0-85085313004OAI: oai:DiVA.org:hb-23349DiVA, id: diva2:1445505
Available from: 2020-06-23 Created: 2020-06-23 Last updated: 2021-10-21Bibliographically approved
In thesis
1. Circular bioeconomy through valorisation of agro-industrial residues by the edible filamentous fungus Neurospora intermedia
Open this publication in new window or tab >>Circular bioeconomy through valorisation of agro-industrial residues by the edible filamentous fungus Neurospora intermedia
2021 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Prevention of dramatic climate change and ensuring food and nutrition security for subsequent generations necessitates the reduction of greenhouse gas emissions and efficient use of the world’s resources, including efficient waste disposal. The agro-industrial sector generates a large amount of organic waste, that is currently underexploited owing to poor waste management practices. The circular bioeconomy model is expected to play an important role in the transition towards a sustainable future, and a group of microorganisms known as fungi can be part of the solution, owing to their ability to convert organic waste into useful products, including both materials and energy. These processes hold great potential to change waste materials into resources, leading to societal and environmental benefits. The versatility of various fungi, including their ability to grow in both submerged and solid states, enables the valorisation of liquid and solid streams such as ethanol plant residues ‘thin stillage’ and surplus bread. However, fungal strains need to produce marketable products and exhibit good growth characteristics to be considered suitable for industrial applications. An interesting candidate is the edible filamentous fungus Neurospora intermedia. This fast-growing fungus is able to grow on a wide array of substrates, in both liquid and solid states, and produce industrially relevant products, including its own nutrient rich fungal biomass and carotenoid pigments. 

Submerged fermentation by N. intermedia in semi-synthetic medium showed that the formation of carotenoids can be enhanced by modulating various factors such as light, low pH, high aeration, and the addition of Mg2+ and Mn2+. When cultivated in thin stillage, 6.3 g/L ethanol was produced, along with protein-rich fungal biomass with potential application as feed. However, an additional step was needed to promote pigment production in the fungal biomass. 

Inspired by the traditional use of N. intermedia for food production by solid-state cultivation, the fungal biomass obtained from cultivation in thin stillage was used as inoculum in a subsequent solid-state fermentation step on surplus bread. The fungal product obtained contained up to 33% proteins and 1.2 mg carotenoids/g total material dry weight. By further combining bread as substrate with brewer’s spent grain, a nutrient-rich fungal-fermented product with an attractive texture was successfully produced. The solid-state cultivation resulted in an improved ratio of essential amino acids, and an increase in dietary fibre, minerals, and vitamins, that added further value to the product. To scale up the process, a novel plug-flow bioreactor was developed and successfully operated semi-continuously, without the addition of an external inoculum. Furthermore, a techno-economic feasibility study of on-site solid-state fermentation in small-scale bakeries revealed that the implementation of this process to sustainably use surplus bread at bakery level is economically feasible. 

These studies lay the foundation for the development of N. intermedia as a tool to convert waste material into useful products, contributing to a fossil fuel-free future with positive impacts on the economy.

Place, publisher, year, edition, pages
Borås: Högskolan i Borås, 2021
Series
Skrifter från Högskolan i Borås, ISSN 0280-381X ; 122
Keywords
Neurospora intermedia, mycoprotein, carotenoids, feed, solid-state fermentation, circular bioeconomy
National Category
Environmental Biotechnology
Research subject
Resource Recovery
Identifiers
urn:nbn:se:hb:diva-25692 (URN)978-91-89271-35-7 (ISBN)978-91-89271-36-4 (ISBN)
Public defence
2021-09-10, C203, Allégatan 1, Borås, 10:00 (English)
Opponent
Supervisors
Available from: 2021-08-16 Created: 2021-06-29 Last updated: 2021-08-16Bibliographically approved

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Gmoser, RebeccaTaherzadeh, Mohammad JLennartsson, Patrik R.

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