The present Thesis regards the role of microrganisms in the process of biodegradation of eco-friendly pots for nursery plant cultivation made from innovative and experimental bioplastics.It is well known that the biodegradability of plastics has become one of the primary topics worldwide for its importance in environmental. If the plastic would remain as it is,we would be inundated with this type of waste for hundreds of years if not thousands of years; the environmental, aesthetic and ecological impact would be devastating. At the end of its use, the plastic vase becomes a refusal to take a few centuries to degrade, becoming, therefore, a serious problem for the environment, especially in many emerging countries where the system of the controlled disposal is not yet active. One of the most important positive aspect of the use of biodegradable polymers in the nursery plant cultivation is the production of a biodegradable pot with competitive costs by using bio-polymers with the addition of organic fillers and/or inorganic waste from other industrial activities. In this way, besides reducing costs, the use of these industrial wastes will be a viable alternative to their current management. In this frame it is essential to replace plastic withbiopolymers, that are those materials which possess biodegrading properties, in particular the capability to be processed under aerobic conditions, into carbon dioxide, water and biomass (or in the case of methane in anaerobic conditions) through a biological process, i.e involves the microorganisms.The production of biodegradable pots and compostable containers represents an area of great commercial and ecological interest, but at the moment there are no commercially available medium and large biodegradable pots able to fully meet the needs of operators in the nursery sector in term of costs,mechanical performance and controlled biodegradability.It's well known that soil microorganisms play a key role in the plant-soil system, enhancing nutrients cycling andavailability, improving soil structure, contrasting plant diseases caused by pathogens and in addition to these important functions soil microorganisms play a crucial role in the biodegradation of bioplastics. Microorganisms (bacteria, fungi, algae) recognize the polymers as a source of organic compounds (eg. Simple monosaccharides, amino acids, etc.) and the energy that sustains them. In other words, the biodegradable polymers are their food. Under the influence of intracellular and extracellular enzymes (endo and exo-enzymes) the polymer degradation enhances chemical reactions through the process of cleavage of the polymer chain. The result of this process, which can be influenced by a large number of different enzymes, are always smaller molecules that enter a cell metabolic process (as in the Krebs cycle), generating energy and turning into water, carbon dioxide, biomass and other basic products of decomposition biotic. In this frame of environmental sustainability the aim of this work thesis is the investigation of the effects of bioplasticsincorporation on the plant-soil microbiota by using DNA-based molecular techniques, such as Denaturing Gradient Gel Electrophoresis (DGGE) and quantitative PCR (qPCR). In the last decades the study of microbial ecology is carried on by themolecular approach based on metagenomic DNA extraction from environmental samples.This approach can give a more complete insight of biodiversity present in an environmentbecause it avoids bias due to laboratory cultivation.In this work thesis, two main different bioplastics were tested, called V101 and V102 with which were made experimental prototypes of biodegradable pots. These bioplastics were composed of selected polymeric materials to whicha nitrogenous organic byproduct, resulting from the shaving of the tanning process, were added as an organic charge. In order to evaluate the effective degradability of these bioplastics and their effect on microbial populations four different tests were set up. To assess the possible effects on soil microorganisms experimental microcosms were set up on a laboratory scale by using increasing concentrations of the two polymers (V101 and V102) in a soil utilized as model. The modifications of the structure and function of bacterial and fungal communities were monitored over time (0, 15, 30, 60, 90 and 150 days from the beginning of the trial). A second experimental design was set up with the objective of evaluating the compostability of the experimental material, by using a composting pile of prototype pots, operating a classic periodic turning mass.Accurate visual investigations indicated that in the vicinity of the tags was not possible to detect any residual trace of both types (V101 and V102) of experimental pots, assuming therefore, only after about a month of composting, a complete biodegradation of the mass constituting the pots. Furthermore, two different compost samples close to V101 e V102 and another compost sample far from them, used as control, were analyzed to investigateresident microbialcommunities. In order to consolidate the qualitative data emerged from the trial composting pile, an experimental system was set up to quantitatively determine, under controlled composting conditions, if V101 e V102 were actually biodegradable, as required by the applicable European standards (UNI EN 13432 and UNI EN 14855-1). Further a plant growth test was set up to verify whether the biodegradation process of biopolymers could have positive or negative effects on growth , by using a fast-growing plant (Lactuca sativa). The effects of these materials were investigated on the microbial populations of the soil-plant system. Results clearly indicated that biopolymers used for the realization of the vessel were effectively compostable;the data obtained from the experimental system of evaluation of the biodegradability, showed a degradation rate even higher than that of the cellulose. Sinceresults indicated a rapid, perhaps excessive, biodegradation process another commercial product, namely bio-plastic Ecovio® firm Basf was tested. The results also confirmed the complete biodegradability of this material, as stated by the manufacturer; however it is possible to note, unlike the materials V101 and V102, a slower rate of biodegradation, so Ecovio® achieved the same levels of biodegradation in a double time. A rapid biodegradation rate, although positive from an environmental point of view, could also adversely affect mechanical and functional performancesof vessels. This rapid degradation is in line with what was observed during the biodegradation test on a laboratory scale (microcosms) about the interaction of these materials with the soil microbial population. The results obtained during these trials, clearly indicated that the two bio-polymers V101 and V102 interact with the soil microbial communities leading to strong modifications of their composition in terms of different populations. These changes do not imply, however, a negative effect as well microcosms containing bio-polymers have a high bacterial and fungal biodiversity. On the contrary, it may be reasonable to assume that the observed stimulation of microbial populations present in the soil-plant system, could lead to a benefit for the growth of plants in pots. In addition, the results of the assessment of the abundance of bacteria and fungi, obtained by qPCR, indicated that the addition of the two bio-polymers to the soil enhances bacterial and fungal growth thus excluding any doubts about a possible effect of inhibition of microbial growth. Also the results obtained by the test on plant growth showed that the effect of "degradation of bioplastics" occurred very close to the plant rootswithoutnegatively affecting their development, allowing the plants not only to complete their growing cycle but to complete it without significant differences with the vegetative cycle of the control plants.In conclusion the use of these biopolymers can be a good business strategy for the nursery industry and at the same time protect the environment. Furthermore clear evidence supports the positive effects of biodegradation of these materials on soil microorganisms and the soil-plant system, suggesting as the future the importance of identifying the populations present in this ecosystem, that are crucial for the whole process of biodegradation.
The present Thesis regards the role of microrganisms in the process of biodegradation of eco-friendly pots for nursery plant cultivation made from innovative and experimental bioplastics. It is well known that the biodegradability of plastics has become one of the primary topics worldwide for its importance in environmental. If the plastic would remain as it is, we would be inundated with this type of waste for hundreds of years if not thousands of years; the environmental, aesthetic and ecological impact would be devastating. At the end of its use, the plastic vase becomes a refusal to take a few centuries to degrade, becoming, therefore, a serious problem for the environment, especially in many emerging countries where the system of the controlled disposal is not yet active. One of the most important positive aspect of the use of biodegradable polymers in the nursery plant cultivation is the production of a biodegradable pot with competitive costs by using bio-polymers with the addition of organic fillers and/or inorganic waste from other industrial activities. In this way, besides reducing costs, the use of these industrial wastes will be a viable alternative to their current management. In this frame it is essential to replace plastic with biopolymers, that are those materials which possess biodegrading properties, in particular the capability to be processed under aerobic conditions, into carbon dioxide, water and biomass (or in the case of methane in anaerobic conditions) through a biological process, i.e involves the microorganisms.The production of biodegradable pots and compostable containers represents an area of great commercial and ecological interest, but at the moment there are no commercially available medium and large biodegradable pots able to fully meet the needs of operators in the nursery sector in term of costs, mechanical performance and controlled biodegradability.It's well known that soil microorganisms play a key role in the plant-soil system, enhancing nutrients cycling and availability, improving soil structure, contrasting plant diseases caused by pathogens and in addition to these important functions soil microorganisms play a crucial role in the biodegradation of bioplastics. Microorganisms (bacteria, fungi, algae) recognize the polymers as a source of organic compounds (eg. Simple monosaccharides, amino acids, etc.) and the energy that sustains them. In other words, the biodegradable polymers are their food. Under the influence of intracellular and extracellular enzymes (endo and exo-enzymes) the polymer degradation enhances chemical reactions through the process of cleavage of the polymer chain. The result of this process, which can be influenced by a large number of different enzymes, are always smaller molecules that enter a cell metabolic process (as in the Krebs cycle), generating energy and turning into water, carbon dioxide, biomass and other basic products of decomposition biotic. In this frame of environmental sustainability the aim of this work thesis is the investigation of the effects of bioplastics incorporation on the plant-soil microbiota by using DNA-based molecular techniques, such as Denaturing Gradient Gel Electrophoresis (DGGE) and quantitative PCR (qPCR). In the last decades the study of microbial ecology is carried on by the molecular approach based on metagenomic DNA extraction from environmental samples. This approach can give a more complete insight of biodiversity present in an environment because it avoids bias due to laboratory cultivation.In this work thesis, two main different bioplastics were tested, called V101 and V102 with which were made experimental prototypes of biodegradable pots. These bioplastics were composed of selected polymeric materials to which a nitrogenous organic byproduct, resulting from the shaving of the tanning process, were added as an organic charge. In order to evaluate the effective degradability of these bioplastics and their effect on microbial populations four different tests were set up. To assess the possible effects on soil microorganisms experimental microcosms were set up on a laboratory scale by using increasing concentrations of the two polymers (V101 and V102) in a soil utilized as model. The modifications of the structure and function of bacterial and fungal communities were monitored over time (0, 15, 30, 60, 90 and 150 days from the beginning of the trial). A second experimental design was set up with the objective of evaluating the compostability of the experimental material, by using a composting pile of prototype pots, operating a classic periodic turning mass. Accurate visual investigations indicated that in the vicinity of the tags was not possible to detect any residual trace of both types (V101 and V102) of experimental pots, assuming therefore, only after about a month of composting, a complete biodegradation of the mass constituting the pots. Furthermore, two different compost samples close to V101 e V102 and another compost sample far from them, used as control, were analyzed to investigate resident microbial communities. In order to consolidate the qualitative data emerged from the trial composting pile, an experimental system was set up to quantitatively determine, under controlled composting conditions, if V101 e V102 were actually biodegradable, as required by the applicable European standards (UNI EN 13432 and UNI EN 14855-1). Further a plant growth test was set up to verify whether the biodegradation process of biopolymers could have positive or negative effects on growth , by using a fast-growing plant (Lactuca sativa). The effects of these materials were investigated on the microbial populations of the soil-plant system. Results clearly indicated that biopolymers used for the realization of the vessel were effectively compostable; the data obtained from the experimental system of evaluation of the biodegradability, showed a degradation rate even higher than that of the cellulose. Since results indicated a rapid, perhaps excessive, biodegradation process another commercial product, namely bio-plastic Ecovio® firm Basf was tested. The results also confirmed the complete biodegradability of this material, as stated by the manufacturer; however it is possible to note, unlike the materials V101 and V102, a slower rate of biodegradation, so Ecovio® achieved the same levels of biodegradation in a double time. A rapid biodegradation rate, although positive from an environmental point of view, could also adversely affect mechanical and functional performances of vessels. This rapid degradation is in line with what was observed during the biodegradation test on a laboratory scale (microcosms) about the interaction of these materials with the soil microbial population. The results obtained during these trials, clearly indicated that the two bio-polymers V101 and V102 interact with the soil microbial communities leading to strong modifications of their composition in terms of different populations. These changes do not imply, however, a negative effect as well microcosms containing bio-polymers have a high bacterial and fungal biodiversity. On the contrary, it may be reasonable to assume that the observed stimulation of microbial populations present in the soil-plant system, could lead to a benefit for the growth of plants in pots. In addition, the results of the assessment of the abundance of bacteria and fungi, obtained by qPCR, indicated that the addition of the two bio-polymers to the soil enhances bacterial and fungal growth thus excluding any doubts about a possible effect of inhibition of microbial growth. Also the results obtained by the test on plant growth showed that the effect of "degradation of bioplastics" occurred very close to the plant roots without negatively affecting their development, allowing the plants not only to complete their growing cycle but to complete it without significant differences with the vegetative cycle of the control plants. In conclusion the use of these biopolymers can be a good business strategy for the nursery industry and at the same time protect the environment. Furthermore clear evidence supports the positive effects of biodegradation of these materials on soil microorganisms and the soil-plant system, suggesting as the future the importance of identifying the populations present in this ecosystem, that are crucial for the whole process of biodegradation.
Tesi di Laurea: Il ruolo dei microrganismi nella biodegradazione di vasi ecocompatibili per il settore florovivaistico / Roberta Prete tesi di Laurea,. - (2014).
Tesi di Laurea: Il ruolo dei microrganismi nella biodegradazione di vasi ecocompatibili per il settore florovivaistico
2014
Abstract
The present Thesis regards the role of microrganisms in the process of biodegradation of eco-friendly pots for nursery plant cultivation made from innovative and experimental bioplastics. It is well known that the biodegradability of plastics has become one of the primary topics worldwide for its importance in environmental. If the plastic would remain as it is, we would be inundated with this type of waste for hundreds of years if not thousands of years; the environmental, aesthetic and ecological impact would be devastating. At the end of its use, the plastic vase becomes a refusal to take a few centuries to degrade, becoming, therefore, a serious problem for the environment, especially in many emerging countries where the system of the controlled disposal is not yet active. One of the most important positive aspect of the use of biodegradable polymers in the nursery plant cultivation is the production of a biodegradable pot with competitive costs by using bio-polymers with the addition of organic fillers and/or inorganic waste from other industrial activities. In this way, besides reducing costs, the use of these industrial wastes will be a viable alternative to their current management. In this frame it is essential to replace plastic with biopolymers, that are those materials which possess biodegrading properties, in particular the capability to be processed under aerobic conditions, into carbon dioxide, water and biomass (or in the case of methane in anaerobic conditions) through a biological process, i.e involves the microorganisms.The production of biodegradable pots and compostable containers represents an area of great commercial and ecological interest, but at the moment there are no commercially available medium and large biodegradable pots able to fully meet the needs of operators in the nursery sector in term of costs, mechanical performance and controlled biodegradability.It's well known that soil microorganisms play a key role in the plant-soil system, enhancing nutrients cycling and availability, improving soil structure, contrasting plant diseases caused by pathogens and in addition to these important functions soil microorganisms play a crucial role in the biodegradation of bioplastics. Microorganisms (bacteria, fungi, algae) recognize the polymers as a source of organic compounds (eg. Simple monosaccharides, amino acids, etc.) and the energy that sustains them. In other words, the biodegradable polymers are their food. Under the influence of intracellular and extracellular enzymes (endo and exo-enzymes) the polymer degradation enhances chemical reactions through the process of cleavage of the polymer chain. The result of this process, which can be influenced by a large number of different enzymes, are always smaller molecules that enter a cell metabolic process (as in the Krebs cycle), generating energy and turning into water, carbon dioxide, biomass and other basic products of decomposition biotic. In this frame of environmental sustainability the aim of this work thesis is the investigation of the effects of bioplastics incorporation on the plant-soil microbiota by using DNA-based molecular techniques, such as Denaturing Gradient Gel Electrophoresis (DGGE) and quantitative PCR (qPCR). In the last decades the study of microbial ecology is carried on by the molecular approach based on metagenomic DNA extraction from environmental samples. This approach can give a more complete insight of biodiversity present in an environment because it avoids bias due to laboratory cultivation.In this work thesis, two main different bioplastics were tested, called V101 and V102 with which were made experimental prototypes of biodegradable pots. These bioplastics were composed of selected polymeric materials to which a nitrogenous organic byproduct, resulting from the shaving of the tanning process, were added as an organic charge. In order to evaluate the effective degradability of these bioplastics and their effect on microbial populations four different tests were set up. To assess the possible effects on soil microorganisms experimental microcosms were set up on a laboratory scale by using increasing concentrations of the two polymers (V101 and V102) in a soil utilized as model. The modifications of the structure and function of bacterial and fungal communities were monitored over time (0, 15, 30, 60, 90 and 150 days from the beginning of the trial). A second experimental design was set up with the objective of evaluating the compostability of the experimental material, by using a composting pile of prototype pots, operating a classic periodic turning mass. Accurate visual investigations indicated that in the vicinity of the tags was not possible to detect any residual trace of both types (V101 and V102) of experimental pots, assuming therefore, only after about a month of composting, a complete biodegradation of the mass constituting the pots. Furthermore, two different compost samples close to V101 e V102 and another compost sample far from them, used as control, were analyzed to investigate resident microbial communities. In order to consolidate the qualitative data emerged from the trial composting pile, an experimental system was set up to quantitatively determine, under controlled composting conditions, if V101 e V102 were actually biodegradable, as required by the applicable European standards (UNI EN 13432 and UNI EN 14855-1). Further a plant growth test was set up to verify whether the biodegradation process of biopolymers could have positive or negative effects on growth , by using a fast-growing plant (Lactuca sativa). The effects of these materials were investigated on the microbial populations of the soil-plant system. Results clearly indicated that biopolymers used for the realization of the vessel were effectively compostable; the data obtained from the experimental system of evaluation of the biodegradability, showed a degradation rate even higher than that of the cellulose. Since results indicated a rapid, perhaps excessive, biodegradation process another commercial product, namely bio-plastic Ecovio® firm Basf was tested. The results also confirmed the complete biodegradability of this material, as stated by the manufacturer; however it is possible to note, unlike the materials V101 and V102, a slower rate of biodegradation, so Ecovio® achieved the same levels of biodegradation in a double time. A rapid biodegradation rate, although positive from an environmental point of view, could also adversely affect mechanical and functional performances of vessels. This rapid degradation is in line with what was observed during the biodegradation test on a laboratory scale (microcosms) about the interaction of these materials with the soil microbial population. The results obtained during these trials, clearly indicated that the two bio-polymers V101 and V102 interact with the soil microbial communities leading to strong modifications of their composition in terms of different populations. These changes do not imply, however, a negative effect as well microcosms containing bio-polymers have a high bacterial and fungal biodiversity. On the contrary, it may be reasonable to assume that the observed stimulation of microbial populations present in the soil-plant system, could lead to a benefit for the growth of plants in pots. In addition, the results of the assessment of the abundance of bacteria and fungi, obtained by qPCR, indicated that the addition of the two bio-polymers to the soil enhances bacterial and fungal growth thus excluding any doubts about a possible effect of inhibition of microbial growth. Also the results obtained by the test on plant growth showed that the effect of "degradation of bioplastics" occurred very close to the plant roots without negatively affecting their development, allowing the plants not only to complete their growing cycle but to complete it without significant differences with the vegetative cycle of the control plants. In conclusion the use of these biopolymers can be a good business strategy for the nursery industry and at the same time protect the environment. Furthermore clear evidence supports the positive effects of biodegradation of these materials on soil microorganisms and the soil-plant system, suggesting as the future the importance of identifying the populations present in this ecosystem, that are crucial for the whole process of biodegradation.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
