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  • 1.
    Akinbomi, Julius
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Brandberg, Tomas
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Sanni, Adebayo
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Taherzadeh, Mohammad
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Development and dissemination strategies for accelerating biogas production in Nigeria2014Ingår i: BioResources, ISSN 1930-2126, E-ISSN 1930-2126, Vol. 9, nr 3, s. 5707-5737Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Following the worsening energy crisis of unreliable electricity and unaffordable petroleum products coupled with the increase number of poverty-stricken people in Nigeria, the populace is desperately in need of cheap alternative energy supplies that will replace or complement the existing energy sources. Previous efforts by the government in tackling the challenge by citizenship sensitization of the need for introduction of biofuel into the country’s energy mix have not yielded the expected results because of a lack of sustained government effort. In light of the shortcomings, this study assesses the current potential of available biomass feedstock for biogas production in Nigeria, and further proposes appropriate biogas plants, depending on feedstock type and quantity, for the six geopolitical zones in Nigeria. Besides, the study proposes government-driven biogas development systems that could be effectively used to harness, using biogas technology, the estimated 270 TWh of potential electrical energy from 181 million tonnes of available biomass, in the advancement of electricity generation and consequent improvement of welfare in Nigeria.

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  • 2.
    Iyer, Sweta
    et al.
    Högskolan i Borås, Akademin för textil, teknik och ekonomi. ENSAIT.
    Behary, Nemeshwaree
    ENSAIT, GEMTEX.
    Nierstrasz, Vincent
    Högskolan i Borås, Akademin för textil, teknik och ekonomi.
    Bio-inspired approaches to design bio-luminescent textiles2017Konferensbidrag (Refereegranskat)
    Abstract [en]

    Luminescent textiles are being increasingly used in apparel and sportswear aswell as in buildings, agriculture and automotives, for safety alert or forillumination or as a design feature[1]. Till now these luminescent textiles havebeen based on technologies such as LED, luminescent particles (rare earthmetals and metal oxides), which are not so eco‐friendly[2].Bio‐inspired strategies can provide efficient methods to achieve eco friendlybioluminescent textiles. Research projects have explored ways which aremainly based on culture of bioluminescent algae[3] or bacteria on textiles.Here we present another approach to achieve bioluminesence using biobasedproducts from various living organisms such as fireflies, fungi, earthwormsthat are found in land and in jelly fishes, shrimps, dinoflagellates, corals inmarine environment [4]. In order to mimic the luminescence effect seen innature, reaction mechanisms in various bioluminescent living organisms arestudied and the components or molecules responsible for luminescence areidentified [5‐10]. Most of the time, these involve enzymatic reactions.However the main challenge is to reproduce the bioluminescent mechanismand to adapt it to new materials which can yield some eco efficient bioinspired luminescent textiles.

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  • 3.
    Rajendran, Karthik
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Björk, Hans
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Taherzadeh, Mohammad J.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Waste Recovery International Partnership: A Model to Transfer Technology and Create Local Development2014Ingår i: Design, Waste & Dignity, CNPq, Olhares , 2014, s. 293-304Kapitel i bok, del av antologi (Övrigt vetenskapligt)
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  • 4.
    Westman, Johan
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Ethanol production from lignocellulose using high local cell density yeast cultures. Investigations of flocculating and encapsulated Saccharomyces cerevisiae2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Efforts are made to change from 1st to 2nd generation bioethanol production, using lignocellulosics as raw materials rather than using raw materials that alternatively can be used as food sources. An issue with lignocellulosics is that a harsh pretreatment step is required in the process of converting them into fermentable sugars. In this step, inhibitory compounds such as furan aldehydes and carboxylic acids are formed, leading to suboptimal fermentation rates. Another issue is that lignocellulosics may contain a large portion of pentoses, which cannot be fermented simultaneously with glucose by Saccharomyces cerevisiae. In this thesis, high local cell density has been investigated as a means of overcoming these two issues. Encapsulation of yeast in semi-permeable alginate-chitosan capsules increased the tolerance towards furan aldehydes, but not towards carboxylic acids. The selective tolerance can be explained by differences in the concentration of compounds radially through the cell pellet inside the capsule. For inhibitors, gradients will only be formed if the compounds are readily convertible, like the furan aldehydes. Conversion of inhibitors by cells close to the membrane leads to decreased concentrations radially through the cell pellet. Thus, cells closer to the core experience subinhibitory levels of inhibitors and can ferment sugars. Carbohydrate gradients also give rise to nutrient limitations, which in turn trigger a stress response in the yeast, as was observed on mRNA and protein level. The stress response is believed to increase the robustness of the yeast and lead to improved tolerance towards additional stress. Glucose and xylose co-consumption by a recombinant strain, CEN.PK XXX, was also improved by encapsulation. Differences in affinity of the sugar transporters normally result in that glucose is taken up preferentially to xylose. However, when encapsulated, cells in different parts of the capsule experienced high and low glucose concentrations simultaneously. Xylose and glucose could thus be taken up concurrently. This improved the co-utilisation of the sugars by the system and led to 50% higher xylose consumption and 15% higher final ethanol titres. A protective effect by the capsule membrane itself could not be shown. Hence, the interest in flocculation was triggered, as a more convenient way to keep the cells together. To investigate whether flocculation increases the tolerance, like encapsulation, recombinant flocculating yeast strains were constructed and compared with the non-flocculating parental strain. Experiments showed that strong flocculation did not increase the tolerance towards carboxylic acids. However, the tolerance towards a spruce hydrolysate and especially against furfural was indeed increased. The results of this thesis show that high local cell density yeast cultures have the potential to aid against two of the major problems for 2nd generation bioethanol production: inhibitors and simultaneous hexose and pentose utilisation.

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  • 5.
    Westman, Johan
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Mapelli, Valeria
    Taherzadeh, Mohammad
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Franzén, Carl Johan
    High local cell density for efficient 2nd generation bioethanol production by Saccharomyces cerevisiae2013Konferensbidrag (Övrigt vetenskapligt)
  • 6.
    Westman, Johan
    et al.
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Mapelli, Valeria
    Taherzadeh, Mohammad
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Franzén, Carl Johan
    Together we are strong: Yeast flocculation for efficient fermentation of toxic hydrolysates2013Konferensbidrag (Övrigt vetenskapligt)
  • 7.
    Ylitervo, Päivi
    Högskolan i Borås, Institutionen Ingenjörshögskolan.
    Concepts for improving ethanol productivity from lignocellulosic materials: encapsulated yeast and membrane bioreactors2014Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    Abstract [en]

    Lignocellulosic biomass is a potential feedstock for production of sugars, which can be fermented into ethanol. The work presented in this thesis proposes some solutions to overcome problems with suboptimal process performance due to elevated cultivation temperatures and inhibitors present during ethanol production from lignocellulosic materials. In particular, continuous processes operated at high dilution rates with high sugar utilisation are attractive for ethanol fermentation, as this can result in higher ethanol productivity. Both encapsulation and membrane bioreactors were studied and developed to achieve rapid fermentation at high yeast cell density. My studies showed that encapsulated yeast is more thermotolerant than suspended yeast. The encapsulated yeast could successfully ferment all glucose during five consecutive batches, 12 h each at 42 °C. In contrast, freely suspended yeast was inactivated already in the second or third batch. One problem with encapsulation is, however, the mechanical robustness of the capsule membrane. If the capsules are exposed to e.g. high shear forces, the capsule membrane may break. Therefore, a method was developed to produce more robust capsules by treating alginate-chitosan-alginate (ACA) capsules with 3-aminopropyltriethoxysilane (APTES) to get polysiloxane-ACA capsules. Of the ACA-capsules treated with 1.5% APTES, only 0–2% of the capsules broke, while 25% of the untreated capsules ruptured within 6 h in a shear test. In this thesis membrane bioreactors (MBR), using either a cross-flow or a submerged membrane, could successfully be applied to retain the yeast inside the reactor. The cross-flow membrane was operated at a dilution rate of 0.5 h-1 whereas the submerged membrane was tested at several dilution rates, from 0.2 up to 0.8 h-1. Cultivations at high cell densities demonstrated an efficient in situ detoxification of very high furfural levels of up to 17 g L-1 in the feed medium when using a MBR. The maximum yeast density achieved in the MBR was more than 200 g L-1. Additionally, ethanol fermentation of nondetoxified spruce hydrolysate was possible at a high feeding rate of 0.8 h-1 by applying a submerged membrane bioreactor, resulting in ethanol productivities of up to 8 g L-1 h-1. In conclusion, this study suggests methods for rapid continuous ethanol production even at stressful elevated cultivation temperatures or inhibitory conditions by using encapsulation or membrane bioreactors and high cell density cultivations.

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    SPIKBLAD01
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