Liguori, Rossana (2016) Development of new Biosystems and Biocatalysts for waste upgrading into the high added value products Bioethanol and Lactic acid. [Tesi di dottorato]

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Item Type: Tesi di dottorato
Lingua: English
Title: Development of new Biosystems and Biocatalysts for waste upgrading into the high added value products Bioethanol and Lactic acid.
Date: 22 April 2016
Number of Pages: 220
Institution: Università degli Studi di Napoli Federico II
Department: Scienze Chimiche
Scuola di dottorato: Biotecnologie
Dottorato: Scienze biotecnologiche
Ciclo di dottorato: 28
Coordinatore del Corso di dottorato:
Faraco, VincenzaUNSPECIFIED
Date: 22 April 2016
Number of Pages: 220
Uncontrolled Keywords: Bioethanol; Lactic acid; Lignocellulosic biomass
Settori scientifico-disciplinari del MIUR: Area 03 - Scienze chimiche > CHIM/11 - Chimica e biotecnologia delle fermentazioni
Date Deposited: 13 Apr 2016 08:42
Last Modified: 22 Apr 2017 01:00


Valorization of lignocellulosic biomass components leads to several possibilities for the production of valuable chemicals, fuels and energy that could be used by modern societies in substitution to conventional ones derived from fossil-based resources. This work was mainly aimed at enlarging the assortment of biosystems and biocatalists (microbes and/or enzymes) for generation of high added value bio-products, such as sugars, ethanol and lactic acid, from both dedicated crops and lignocellulosic wastes. Particularly, 32 different fungal strains, belonging to the collection of the Department of Engenharia de Bioprocessos e Biotecnologia (University Federal do Paraná, Brasil) (DEBB), were investigated for ligninolytic, cellulolytic and xylanolytic activities production on solid and liquid media. The screening led to the selection of Aspergillus niger NRRL 3312, as the best cellulase and xylanase activities producer and the strain Pleurotus sajor-caju INRA 3501 for the laccase activity production. Brewers' spent grain (BSG) was shown a suitable substrate for the low cost lignocellulolytic enzymes production by solid state fermentation with the selected strains; indeed, A. niger NRRL 3312 reached a maximum cellulase and xylanase activities production of 118.04 U gram-1 of dry substrate (gds) and 1315.15 U gds-1, respectively, wilst P. sajor-caju INRA 3501 showed a maximum laccase production of 157.36 U gds-1. By proteomic analyses peptides belonging to the enzymes responsible for the cellulase and xylanase activities from A. niger NRRL 3312 and for the laccase acitivity from P. sajor-caju INRA 3501 were identified. An enzymatic mixture of cellulases and xylanases, produced by the strain Pleurotus ostreatus using microcrystalline cellulose as inducer, was partially characterized and tested in the statistical analysis of Arundo donax saccharification. The Plackett-Burman screening design, applied to identify the most significant parameters for the maximum sugars release, showed that the most significant influence was exercised by temperature, pH, and time. The combined effect of these factors on the saccharification process was analyzed by a 33 factorial experimental design and the best result of 480.10 mg of sugars gds-1 was obtained at 45 °C, pH 3.5, and 96 hours of incubation. Alkaline-acid (AAT) pretreated BSG was evaluated for ethanol production after enzymatic hydrolysis with commercial enzymes. The obtained hydrolysate, with a glucose concentrationn of 75 g/L, diluted to 50 g/L, was used for fermentation by the strain Saccharomyces cerevisiae NRRL YB 2293, selected as the best producer among five ethanologenic microorganims belonging to the DEBB collection. When the hydrolysate was supplemented with yeast extract, 12.79 g/L of ethanol, corresponding to 55 % of the maximum theoretical value, was obtained within 24 hours, while in the non-supplemented hydrolysate, a similar concentration was reached within 48 hours; indeed, the added nitrogen source reduced the ethanol fermentation time and promoted glucose uptake and cell growth. Lactobacillus acidophilus ATCC 43121, selected as the best lactic acid producer among six Lactobacillus strains belonging to the DEBB collection, was analyzed for its ability to grow on the hydrolysates obtained from BSG after AAT or aqueous ammonia soaking (AAS) pretreatment. The lactic acid production by L. acidophilus ATCC 43121 through fermentation of the hydrolysate from AAS treated BSG was 96 % higher than that from the AAT treated one, although similar yields of lactic acid per consumed glucose were achieved. The best results were obtained by fermentation of AAS BSG hydrolysate supplemented with yeast extract, in which the strain produced 22.16 g/L of lactic acid (yield of 0.61 g/g), 27 % higher than the value (17.49 g/L) obtained in the absence of a nitrogen source.


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