Lignocellulolytic enzymes production via solid-state fermentation of agroindustrial residues: process optimization and application
- Autores: Jordi Llimós Turet
- Directores de la Tesis: Sergio Ponsá Salas (dir. tes.), Oscar Mauricio Martínez Avila (codir. tes.)
- Lectura: En la Universitat de Vic - Universitat Central de Catalunya ( España ) en 2022
- Idioma: inglés
- Tribunal Calificador de la Tesis: Adriana Artola Casacuberta (presid.), María Isabel Mora Garrido (secret.), Joan Dosta Parras (voc.)
- Programa de doctorado: Programa de Doctorado en Ciencias Experimentales y Tecnologías / Experimental Sciences and Technology por la Universidad de Vic-Universidad Central de Catalunya
- Materias:
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- Resumen
This thesis is focused on the valorisation of agro-industrial waste through the use of solid-state fermentation (SSF) for enzyme production. This study was developed as part of the project Valorización de residuos agroindustriales para la producción de Bioplásticos (VALORA, CTM2016-81038-R) and it is the first study on SSF developed within the BETA Tech Center. The study has focused on the use of three different wastes from the food industry (brewer’s spent grain, grape pomace and olive-mill solid waste) as potential substrates for the production of lignocellulolytic enzymes. These lignocellulosic-derived wastes are produced in large quantities in important local industries within Catalonia region, and their management still generates some environmental problems. However, these residues have properties that make them interesting as a source of lignocellulolytic enzymes, and therefore they can be potentially valorised by obtaining a high value-added product. In order to achieve this goal, three fungal strains have been evaluated as enzyme producers: Aspergillus niger, Thermoascus aurantiacus and Trichoderma reesei. Chapter 4 sets out the selection of the substrate for enzyme production within the three selected residues. After the substrate was selected, a preliminary study was performed to determine the potential for producing lignocellulolytic enzymes from the three abovementioned fungal strains. In order to evaluate such a potential, the enzymatic activities served as the main performance parameter. Nevertheless, the efficiency of the obtained extracts to release sugars was also tested. Finally, a proof of concept was carried out, in line with the objective of the VALORA project to produce biodegradable bioplastics (polyhydroxyalkanoates) starting from the fermentable sugars produced with the enzymes. In a second stage, it was decided to continue working with two of the evaluated strains (A. niger and T. aurantiacus) to optimise the enzymatic production process at lab scale (Chapter 5). The A. niger SSF performed at the optimal conditions found a maximum xylanase activity value of 309.0 ± 24.5 U·g-1DM at 42 h and a maximum cellulase activity value of 7.9 ± 1.0 FPU·g-1DM at 24 h. The T. aurantiacus SSF performed at the optimal conditions found a maximum xylanase activity value of 156.1 ± 15.8 U·g-1DM at 48 h and a maximum cellulase activity value of 3.5 ± 0.5 FPU·g-1DM at 48 h. Once the process was optimised, a change of scale was made in order to study the process at bench scale and to evaluate different reactor configurations (Chapter 6). The best results were obtained using A. niger with the PVC reactors with a maximum xylanase activity (245.5 ± 21.6 U·g-1DM, 5.1 ± 0.5 U·g-1DM·h-1 of productivity) at 48 h and a maximum cellulase activity (4.5 ± 0.2 FPU·g-1DM, 0.06 ± 0.00 FPU·g-1DM·h-1 of productivity) at 80 h. Finally, the most promising extracts obtained during the study were subjected to different tests to assess their efficiency in the hydrolysis of diverse materials. In that step, it was also included the solid fraction of steam exploded materials as attempt to evaluate the enzymatic extracts in a wider range of materials (Chapter 7) and these were hydrolysed both in liquid and solid media. In general, the results presented in this thesis constitute a first approach toward the use of SSF and pure fungal strains as a valid technology for the production of enzymes of industrial interest using low-cost raw materials.This thesis is focused on the valorisation of agro-industrial waste through the use of solid-state fermentation (SSF) for enzyme production. This study was developed as part of the project Valorización de residuos agroindustriales para la producción de Bioplásticos (VALORA, CTM2016-81038-R) and it is the first study on SSF developed within the BETA Tech Center. The study has focused on the use of three different wastes from the food industry (brewer’s spent grain, grape pomace and olive-mill solid waste) as potential substrates for the production of lignocellulolytic enzymes. These lignocellulosic-derived wastes are produced in large quantities in important local industries within Catalonia region, and their management still generates some environmental problems. However, these residues have properties that make them interesting as a source of lignocellulolytic enzymes, and therefore they can be potentially valorised by obtaining a high value-added product. In order to achieve this goal, three fungal strains have been evaluated as enzyme producers: Aspergillus niger, Thermoascus aurantiacus and Trichoderma reesei. Chapter 4 sets out the selection of the substrate for enzyme production within the three selected residues. After the substrate was selected, a preliminary study was performed to determine the potential for producing lignocellulolytic enzymes from the three abovementioned fungal strains. In order to evaluate such a potential, the enzymatic activities served as the main performance parameter. Nevertheless, the efficiency of the obtained extracts to release sugars was also tested. Finally, a proof of concept was carried out, in line with the objective of the VALORA project to produce biodegradable bioplastics (polyhydroxyalkanoates) starting from the fermentable sugars produced with the enzymes. In a second stage, it was decided to continue working with two of the evaluated strains (A. niger and T. aurantiacus) to optimise the enzymatic production process at lab scale (Chapter 5). The A. niger SSF performed at the optimal conditions found a maximum xylanase activity value of 309.0 ± 24.5 U·g-1DM at 42 h and a maximum cellulase activity value of 7.9 ± 1.0 FPU·g-1DM at 24 h. The T. aurantiacus SSF performed at the optimal conditions found a maximum xylanase activity value of 156.1 ± 15.8 U·g-1DM at 48 h and a maximum cellulase activity value of 3.5 ± 0.5 FPU·g-1DM at 48 h. Once the process was optimised, a change of scale was made in order to study the process at bench scale and to evaluate different reactor configurations (Chapter 6). The best results were obtained using A. niger with the PVC reactors with a maximum xylanase activity (245.5 ± 21.6 U·g-1DM, 5.1 ± 0.5 U·g-1DM·h-1 of productivity) at 48 h and a maximum cellulase activity (4.5 ± 0.2 FPU·g-1DM, 0.06 ± 0.00 FPU·g-1DM·h-1 of productivity) at 80 h. Finally, the most promising extracts obtained during the study were subjected to different tests to assess their efficiency in the hydrolysis of diverse materials. In that step, it was also included the solid fraction of steam exploded materials as attempt to evaluate the enzymatic extracts in a wider range of materials (Chapter 7) and these were hydrolysed both in liquid and solid media. In general, the results presented in this thesis constitute a first approach toward the use of SSF and pure fungal strains as a valid technology for the production of enzymes of industrial interest using low-cost raw materials.
