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Innovative biotechnological process for the conversion of lignocellulosic biomasses into high added-value products.
No full textClimate change and environment degradation are an concrete threats for the world. To overcome these threats, the European Union (EU) has put in place the European Green Deal (EGD), a growth strategy aimed at developing an EU competitive and sustainable economy. The EGD, adopted at the end of 2019, provides the action plan to achieve the carbon neutrality, resource efficiency and zero pollution in the EU by 2050. This set of policy initiatives, coupled with the new EU Recovery Plan developed to support the repair of the economic and social damages caused by the COVID-19 pandemic, represents today the most crucial milestones in the green transition towards a more resilient, competitive and environmentally sustainable Europe. The transition from a fossil-based economy to a bio-based economy is necessary to guarantee a sustainable future for the society. In this sense, the development of biorefinery processes able to replace traditional fossil processes has attracted great attention. Biorefineries are technological platforms making use of both biotechnological and/or chemical processes to convert different bioresources into a spectrum of high value-added products. One of the most widespread and consolidated biomass biorefinery processes concerns the production of first-generation biofuels from vegetable oils, but the environmental externalities due to the intensive cultivation of oil crops has led several European countries to discourage the use of some vegetable oils for biofuels production. An excellent, green, and sustainable alternative to vegetable oils is represented by microbial oils produced by oleaginous microorganisms.
Some microorganisms are defined oleaginous in consequence of their ability to accumulate lipids for over 20% of their dry cellular weight. This group includes several eukaryotic microorganisms (such as fungi, yeasts and algae) and some species of autotrophic and heterotrophic bacteria able to accumulate lipids in the form of triglyceride (TAG). Among these, the yeasts are considered the best candidates for industrial processes thanks to their rapid growth, the ability to utilize a wide variety of raw materials and the easy cultivation in large fermenters. The lipids produced by oleaginous yeasts, better known as Single Cell Oil (SCOs), have a composition very similar to vegetable oils, with a predominance of oleic acid (18:1), followed by palmitic acid (C16:0), linoleic acid (C18:2), and stearic acid (C18:0). Of the 1500 known species belonging to 100 different genera, about 30 of them are capable of accumulating lipids, and the most known oleaginous yeasts include the genera Yarrowia, Rhodotorula (Rhodosporidium), Lipomyces, and Cryptococcus. SCOs may serve as a renewable source of edible oil and as an intermediate ‘‘building block’’ for oleochemicals, including: fuels, soaps, plastics, paints, detergents, textiles, rubber, surfactants, lubricants, additives for the food and cosmetic industry and many other chemicals.
Although the use of SCOs as a feedstock for biofuels and biochemicals has received interest in recent years, high production costs, estimated in the range 4.1 and 5.8 $ / kg, prevented their industrial applications. Using low-cost carbon sources together with more efficient bioconversion processes could make this process more competitive.
Several types of waste and low-cost carbon sources, including olive mill wastewater, and by-products of the dairy industry, food processing, and lignocellulosic residues have been used as feedstock to produce microbial lipids. Due to the high content of inorganic material, widely available lignocellulosic residues such as agricultural straws could be more suitable to achieve fermentable sugars with respect to produce heat and electricity through thermal processes. Due to their recalcitrant nature, lignocellulosic biomasses require pre-treatments to favour the breakdown of the lignin structural matrix and favour the enzymatic hydrolysis of polysaccharides. Pre-treatment involves the application of physical, chemical, biological or physicochemical approaches, among which steam explosion has been recognized as one of the most effective, economical and sustainable processes. The main limit of this technology is the formation of thermal degradation by-products, such as 5-hydroxymethylfurfural (5-HMF), furfural, weak acids, and phenols. These molecules could inhibit the growth of most microorganisms. For these reasons scientific efforts are aimed at identifying robust microorganisms able of tolerating the stress induced by these molecules. In addition, genetic engineering, adaptive evolutionary techniques, and fermentation strategies could improve the specific microorganism resistance and increase the process yields.
This PhD was supported by regional government in the framework of the industry 4.0 strategy and, in order to meet the needs of the Basilicata region, the main objective of this PhD activity was the development of a process which might be useful for regional economy. By considering the strong agricultural vocation of Basilicata region and the presence in this area of one of the largest oil fields in Europe, this PhD project was aimed to develop a biorefinery process for valorisation of agricultural wastes, for the production of high added-value products. The development of a biorefinery process useful for enhancing the local agriculture by-products represents a green and sustainable alternative to classic petrochemical processes.
The aim of this Ph.D. thesis was the investigation and the optimization of innovative processes to convert lignocellulosic residues into microbial oils at industrial relevant conditions. In fact the profitable conversion of lignocellulosic biomass into biobased products through the platform sugars requires the intermediate production of concentrated biomass hydrolysates that, however, could contain many microbial inhibitors. The development of optimized bioconversions processes could alleviate the production costs for the hydrolysates detoxification. In particular, the research work concerned the conversion of second-generation sugars through previously optimized processes of steam pretreatment and enzymatic hydrolysis of wheat straw and cardoon residues into microbial oils. Teste microorganisms included oleaginous yeasts belonging to the species Cutaneotrichosporon curvatus CA-3802, Lipomyces tetrasporus Li-0407, and Yarrowia lipolytica ATCC 46483. Many fermentation set-up were developed to overcome the inhibition induced by thermal degradation by-products and maximize the conversion yields. The fermentation process optimized in shaken flasks was then scaled-up in the 2, 10 and 50 L stirred tank bioreactor. According to sustainable chemistry strategies and to improve the economic feasibility of the process, the downstream phase was implemented through the use of sustainable and non-hazardous solvents. Furthermore, the suitability of the microbial oil versus target applications was investigated for the production of biodiesel, green diesel and polyurethanes. Finally, on the basis of the biorefinery process developed in this Ph.D. thesis, a technical-economic analysis was carried out.
Specific aims of the research project were the following:
I. To study and optimize the growth of oleaginous yeasts in simulated medium and un-detoxified biomass hydrolysates, and improvement of the microbial conversion in order to produce high-titer lipids;
II. scale-up of the biorefinery process from laboratory to pilot scale;
III. evaluate an innovative extraction mixture and synthesize high added-value products, such as intermediates for the food and oleochemical industries;
IV. to evaluate the overall economic feasibility of the implemented process through a technical-economic analysis;
In particular, Chapter I describes the state of the art of the proposed process with particular interest on the use of oleaginous yeasts for the production of SCOs.
Chapters II and III describe the microbial conversion of undetoxified lignocellulosic hydrolysates, such as cardoon residues hydrolysate and wheat straw hydrolysate, by the use of Cutaneotrichosporon curvatus CA-3802, Lipomyces tetrasporus Li-0407, and Yarrowia lipolytica ATCC 46483. The activities were focused on the process conditions useful to overcome the inhibition induced by the biomass degradation products. Furthermore, the microbial lipids obtained were characterized and converted into high added-value products.
Chapter IV describe the implementation of economic feasibility and scale-up of the process. The first step was addressed to the optimization of enzymatic hydrolysis process of steam pretreated wheat straw in order to enhance economic feasibility of the process through the decrease of the enzymatic load. Subsequently, cheap nitrogen sources were also evaluated in the lipid synthesis phase. The scale-up of the process was carried out in pilot scale 50 L bioreactor.
Lipids extraction and synthesis of high added-value products were described in Chapter V. An innovative extraction solvent was studied. Microbial lipids produced were converted into advanced fuels for hydrocarbon industry and microbial bioplastics.
Finally, the technical-economic analysis of the proposed biorefinery process was described in Chapter VI
L'ORIENTAMENTO AL MARKETING PER LA RIVITALIZZAZIONE DELL'INDUSTRIA DELLA VERNACCIA DI ORISTANO
No full textBehaviour of grape must fermentation by Saccharomyces cerevisiae cells immobilized within insolubilized gelatin
No full textSaccharomyces cerevisiae strains, commonly used in Vermentino grape must fermentation were entrapped in polyaldehyde gelatine discs by obtaining three different types of immobilizates which were assayed for fermentative activity. The cells immobilized as a biofilm produced more ethanol than normal, but cell release, although delayed, was not prevented, not even by coating the discs with an additional gel layer
A culture-independent PCR-based method for the detection of Lachancea thermotolerans in wine
No full textWhen inoculated in association with Saccharomyces cerevisiae, the yeast Lachancea thermotolerans determines a reduction of volatile acidity and an increase in the production of glycerol, 2-phenylethanol, and polysaccharides. Moreover, L. thermotolerans is a natural L-lactic acid producer, thus it contributes to wine acidification and microbiological stabilization. In view of its utilization in winemaking, a culture-independent PCR-based method was developed for the detection of L. thermotolerans during wine fermentations. This method, which utilizes species-specific PCR primer pairs that anneal to intron 2 of the mitochondrial COX1 gene, is rapid and reliable, and detects L. thermotolerans in wine at 104 cells/ml and with a S. cerevisiae/L. termotholerans ratio of 1,000/1
Valorisation of olive pomace and tomato by-products with selected yeasts strains
No full textFood industries produce high amounts of by-products, wastes and residues which are considered a problem because they contribute to environmental pollution. On the other hand, by-products are generally rich in various nutrients and functional compounds, e.g., dietary fibres and/or bioactive components such as flavonoids and polyphenols recognized as antimicrobial and anti-radical compounds. A possible strategy for their valorization is their use as feedstock for microbial fermentation by selected strains of yeast and lactic acid bacteria (LAB) for the production of valuable bio-based compounds. In particular, in this study olive pomace (OP) and tomato residues and seeds (TR) were analyzed, and 31 strains of yeasts were isolated from OP and 30 from TR. In addition, more than 50 strains of LAB were isolated from TR. Yeasts were characterized for some metabolic features such as lipase, protease and beta-glucosidase activities. When grown in culture media with OP or TR as the only nutrient source, marked lipolytic and proteolytic activities were shown by some yeast strains already after 2 days of incubation at 30°C. Moreover, more than 60 volatile compounds interesting for the food, cosmetics or chemical sectors were detected by GC/MS-SPME analysis. In particular, several molecules used as food flavouring or perfume compounds were identified. In conclusion, the results obtained indicate that the tested biotechnological approach can be a promising strategy for the exploitation of polluting by-products through the production of bio based flavours. From a technological point of view, the yeast isolates could be also exploited for bioremediation of olive oil wastewaters or as a source of enzymes of biotechnological interest
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Behaviour of Saccharomyces cerevisiae wine strains during adaptation to unfavourable conditions of fermentation on synthetic medium: Cell lipid composition, membrane integrity, viability and fermentative activity
No full textDuring must fermentation wine strains are exposed to a variety of biotic and abiotic stresses which, when prevailing over the cellular defence systems, can affect cell viability with negative consequences on the progression of the fermentative process. To investigate the ability of wine strains to survive and adapt to unfavourable conditions of fermentation, the lipid composition, membrane integrity, cell viability and fermentative activity of three strains of Saccharomyces cerevisiae were analysed during hypoxic growth in a sugar-rich medium lacking lipid nutrients. These are stressful conditions, not unusual during must fermentation, which, by affecting lipid biosynthesis may exert a negative effect on yeast viability. The results obtained showed that the three strains were able to modulate cell lipid composition during fermentation. However, only two of them, which showed highest viability and membrane integrity at the end of the fermentation process, reached a fatty acid composition which seemed to be optimal for a successful adaptation. In particular, C16/TFA and UFA/TFA ratios, more than total lipid and ergosterol contents, seem to be involved in yeast adaptation. © 2007 Elsevier B.V. All rights reserved
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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