Improving the efficiencies of photoautotrophic biofuel production: from biomass to biocatalysts

The rising effects of climate change and global problems of resource scarcity and environmental pollution require a change in paradigm towards sustainable energy and chemicals production. Photosynthetic microbes, including cyanobacteria and green algae, are promising raw materials for future production platforms which have high aerial productivity and don’t compete with food and feed. They are also well suited to act as chassis for the direct and continuous production of targeted fuels and chemicals, thus functioning as true biocatalysts. However, efficiencies of photoautotrophic production system need improvement before a successful shift to these platforms. The overall aim of this thesis is to improve efficiencies of photoautotrophic production platforms. To meet this aim, I have studied two approaches: (i) Integrative biomass-based production; and (ii) Direct biofuel/chemical production. The first approach involved the integration of wastewater treatment with biofuel production, using native Finnish microalgae. Screening revealed the native alga UHCC0027 as a suitable candidate for efficient nutrient removal and lipid accumulation. At pilot scale, UHCC0027 demonstrated robust nutrient removal performance in real wastewater of both high and low organic loading and at different temperatures, including a cold temperature relevant to Nordic conditions. Nutrient balances (C:N and N:P) were important in biomass accumulation and nutrient removal performance. Whilst Fatty acid methyl ester (FAME) profiles did not meet requirements of unblended fuel standards, workarounds such as hydrogenation may succeed in future. The second approach involved the immobilization of cyanobacterial and green algal cells in a novel tunable immobilization material, TEMPO oxidized cellulose nanofibrils (TEMPO CNF). This transfers the capabilities of current suspension photosynthetic cell factories to a solid-state that restricts loss of energy to biomass accumulation and enables photosynthetic cells to operate as long-living true catalysts for bioproduction. Three different construction methods were used: (i) a pure TEMPO CNF hydrogel; (ii) a Ca2+-stabilized TEMPO CNF hydrogel; and (iii) a polyvinyl alcohol (PVA) crosslinked solid TEMPO CNF film. Important outcomes were the considerably higher hydrogen yields of TEMPO CNF immobilized Chlamydomonas reinhardtii (compared to alginate controls) and the recovery and efficient hydrogen production of Anabaena sp. PCC7120 ΔhupL cells after drying. Drying was required for stable film formation and presents an opportunity for scaffold-free films in future. Overall, this thesis presents work demonstrating promising optimizations for improving efficiencies of microalgal wastewater treatment and biofuel (chemicals) production. Additionally, the novel employment of TEMPO CNF immobilization matrix for photobiological hydrogen production is an important step to addressing porosity and mechanical stability limitations of current immobilization techniques.Yhä kasvavat ilmastonmuutoksen, resurssiniukkuuden ja ympäristön saastumisen aiheuttamat haitat vaativat uutta kestävämpää tapaa energian ja kemikaalien tuotantoon. Yhteyttävät mikrobit, jotka sisältävät syanobakteerit ja viherlevät, ovat lupaavia lähtöaineita niiden tuotantoon, koska niiden tuotto pinta-alaa kohden on suuri, eikä niiden kasvatus kilpaile ruuantuotannon kanssa. Lisäksi ne soveltuvat haluttujen polttoaineiden ja kemikaalien tuotantoon eräänlaisina biokatalyytteinä, jolloin solu tuottaisi näitä lopputuotteita ilman erillistä jalostusvaihetta. Kuitenkin tarvitaan vielä merkittäviä parannuksia tuottotehokkuuteen, jotta näiden biokatalyyttien teollinen käyttö tulisi kannattavaksi. Väitöskirjan aiheena on tehostaa yhteyttävien mikrobien tehokkuutta eri sovelluksissa. Tämän tavoitteen saavuttamiseksi työssä tutkittiin kahta eri lähestymistapaa: (i) yhdistetty biomassapohjainen tuotanto ja (ii) suora biopolttoaine-/kemikaalituotanto. Ensimmäisessä lähestymistavassa sovellettiin yhdistettyä jätevedenpuhdistusta ja biopolttoaineiden tuotantoa hyödyntäen suomalaisia mikroleväkantoja. Leväkantojen seulonnassa UHCC0027 levälaji osoittautui lupaavaksi ravinteiden kerääjäksi. Lisäksi se oli tehokas rasvapitoisuuden keräämisessä. Pilotti-mittakaavassa se osoitti tehokasta ravinteiden sitomista oikeassa jätevedessä useissa eri olosuhteissa (mm. korkea ja matala orgaanisen aineen pitoisuus ja eri lämpötilat). Ravinteiden suhteilla (C:N ja N:P) oli tärkeä rooli biomassan kasvussa ja ravinteiden sitomisnopeudessa. Rasvahappojen metyyliesterien profiilit eivät täyttäneet sekoittamattoman biodieselin vaatimuksia, mikä voidaan välttää esimerkiksi hydrogenoimalla rasvahapot. Toinen lähestymistapa oli syanobakteerien ja viherleväsolujen immobilisointi TEMPO-hapetettuihin selluloosa nanofibrilleihin (TEMPO CNF), mikä tehtiin ensimmäistä kertaa tämän väitöskirjatyön puitteissa. Immobilisointi mahdollistaa useimmiten käytettyjen liuosmaisten kasvatusten siirtämisen kiinteään matriisiin. Tämä puolestaan tehostaa solujen energiatehokkuutta lopputuotteiden suuntaan, kun solujen jakaantuminen saadaan pysäytettyä. Lisäksi immobilisointi säilyttää fotosynteettisten solujen biokatalyyttisen aktiivisuuden pidempään. Tässä lähestymistavassa käytettiin kolmea eri metodia: (i) puhdas TEMPO CNF hydrogeeli; (ii) Ca2+-ioneilla stabilisoitu TEMPO CNF hydrogeeli; ja (iii) polyvinyylialkoholilla (PVA) ristisilloitettu kiinteä TEMPO CNF filmi. Tärkeimpiä tuloksia olivat TEMPO CNF immobilisoitujen Chlamydomonas reinhardtii viherlevien korkeampi vedyntuotto (verrattuna alginaatti verrokkiin) ja Anabaena sp. PCC7120 ΔhupL solujen tehokas vedyntuotto kuivausvaiheen jälkeen. Kuivausvaihe tarvittiin jäykän ja vahvan filmin aikaansaamiseksi. Yhteenvetona voidaan todeta, että tämä väitöskirjatyö osoitti lupaavia tapoja mikrolevillä tehtävän jätevedenpuhdistuksen ja biopolttoaineiden tuotannon tehostamiseksi. Lisäksi ensikertaa mikroleväsolujen immobilisointiin käytetyllä TEMPO CNF nanoselluloosalla on monia ominaisuuksia, kuten huokoisuus ja mekaaninen vahvuus, jotka parantavat biokatalyyttien tuottotehokkuutt

Screening native isolates of cyanobacteria and a green alga for integrated wastewater treatment, biomass accumulation and neutral lipid production

The value and efficiency of microalgal biofuel production can be improved in an integrated system using waste streams as feed-stock, with fuel-rich biomass and treated wastewater being key end-products. We have evaluated seven native cyanobacterial isolates and one native green alga for their nutrient removal, biomass accumulation and lipid production capacities. All native isolates were successfully grown on synthetic wastewater mimicking secondary treated municipal wastewater (without organic carbon). Complete phosphate removal was achieved by the native green alga, isolated from Tvarminne (SW Finland). Optimisation of the C:N ratio available to this strain was achieved by addition of 3% CO2 and resulted in complete ammonium removal in synthetic wastewater. The native green alga demonstrated similar nutrient removal rates and even stronger growth in screened municipal wastewater, which had double the ammonium concentration of the synthetic media and also contained organic carbon. Sequencing of the genes coding for 18S small rRNA subunit and the ITS1 spacer region of this alga placed it in the Scenedesmaceae family. The lipid content of native isolates was evaluated using BODIPY (505/515) staining combined with high-throughput flow cytometry, where the native green alga demonstrated significantly greater neutral lipid accumulation than the cyanobacteria under the conditions studied. (C) 2015 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).Peer reviewe

Value-at-risk - models in extreme market conditions

Value-at-Risk has widely been accepted as the standard measure of market risk in the past twenty years. Nonetheless, VaR models are useful insofar they forecast market risk with sufficient accuracy. The excessive number of losses over VaR limits observed during the recent financial crisis of 2008 revealed that VaR might not necessarily be an accurate measure of risk during times of market uncertainty. The objective of this thesis is to evaluate the performance of various VaR models in high volatility market conditions. The research question could be formed as: are VaR models sufficiently accurate in high volatility market conditions to justify their use as the standard market risk metric? The research question should be given extra attention as VaR is part of the current financial regulation. The theoretical part of the thesis presents the basic VaR models, as well as some of the formal backtests which are used to evaluate the accuracy of the computed VaR estimates in the empirical part of the thesis. In addition, some of the main critique toward VaR will be reviewed. The empirical part of the thesis concentrates on evaluating the accuracy of the presented VaR models during the years 2007-2009 with data of two stock indices. Evaluation of model performance is based on backtesting the frequency as well as the independence of the VaR exceptions. The results show that most VaR models in this thesis underestimated market risk during the backtesting period of 2007-2009. In particular, poor performance was observed with parametric VaR models, and with the basic Historical Simulation. The results indicate that the parametric models are highly sensitive regarding the assumptions behind the model, which can be considered as the main drawback of the method. On the basis of the results, combining a sophisticated volatility estimation technique with the Historical Simulation provides an accurate model for risk forecasting during times of high market volatility. Therefore, the future reliance on VaR should be based on these type of models