Date of Defense
25-11-2024 2:30 PM
Location
F3-032
Document Type
Thesis Defense
Degree Name
Master of Science in Horticulture
College
College of Agriculture and Veterinary Medicine
Department
Integrative Agriculture
First Advisor
Dr. Elke Gabriel Neumann
Keywords
Food security, crop residues, heterotrophic plant cultures, bioreactors, root organ cultures
Abstract
All agricultural plant production requires investment of water, energy, and land, especially in the Gulf Region, where environmental conditions are not ideally suitable for crop farming. Currently, less than 40 % of agricultural produce constitutes food, which greatly limits the overall feasibility of food production systems worldwide. Crop residues contribute more than half to global agricultural plant production, and food waste and biomass from public parks and gardens further add to the vast pool of non-edible plant material. Existing valorization strategies for such material cannot compensate for the enormous amounts of water, energy, land, and human resources invested in their production. A comparatively small portion of non-edible plant biomass is suitable as feed for farm animals and can be converted into animal products at ratios of typically 7 – 10 %. Given the poor conversion efficiency and high greenhouse gas emissions of animal production systems, innovative solutions for conversion of non-edible into edible biomass are urgently required. The present study tested the concept of conversion of non-edible crop residues into edible plant material via heterotrophic plant organ cultures rather than farm animals. Following acid, enzymatic, or microbial hydrolysis, cellulosic waste could be converted into a mixture of monosaccharides, dominated by glucose. The present study characterized the ability of in vitro crop root organ cultures to utilize externally provided sugars for growth, thus converting soluble carbohydrates into edible plant biomass. Results revealed that plant species differ in their heterotrophic capabilities. When grown on sucrose, basil roots were able to convert up to 70% of the supplied carbon into their biomass. Conversion rates on media based on glucose were slightly less efficient compared with those based on sucrose, but still achieved conversion rates of up to 50 %. The efficiency by which cellulosic plant material can be converted into sugars typically lies in the range of 50 – 70 %. Based on this and the results of the present study, root organ cultures would achieve an overall conversion efficiency of 25 – 30 %, far outperforming farm animals and other existing bioreactor-based conversion systems, e.g., based on cell cultures, bacteria, or algae. The present study identified likely opportunities for further improvement of this conversion system. As revealed by the mineral element analysis of the root organ cultures, the Ca and P supply of these plant tissues likely limited their growth performance. Future studies should elucidate reasons for this and develop strategies for increasing the availability of these elements to in vitro root cultures. A comparison of different gelling agents and physical properties of the growth medium revealed only small differences, suggesting that the gelling agent type and strength are not major determinants of culture performance. Liquid cultures did not differ from those on solid media in their ability to utilize sucrose for growth. Further improvement of the conversion efficiency can likely be achieved by culture aeration, e.g. through forced ventilation. Based on the present findings, T-DNA transformation of root organs is not a prerequisite to achieving high biomass conversion rates. In non-transformed, adventitious roots supplied with IBA, the conversion efficiency likely increases with an increasing number of explants added to the culture medium.
Included in
Evaluation of opportunities for the cultivation of heterotrophic plant root organ cultures as food: Optimization of culture conditions and carbohydrate sources
F3-032
All agricultural plant production requires investment of water, energy, and land, especially in the Gulf Region, where environmental conditions are not ideally suitable for crop farming. Currently, less than 40 % of agricultural produce constitutes food, which greatly limits the overall feasibility of food production systems worldwide. Crop residues contribute more than half to global agricultural plant production, and food waste and biomass from public parks and gardens further add to the vast pool of non-edible plant material. Existing valorization strategies for such material cannot compensate for the enormous amounts of water, energy, land, and human resources invested in their production. A comparatively small portion of non-edible plant biomass is suitable as feed for farm animals and can be converted into animal products at ratios of typically 7 – 10 %. Given the poor conversion efficiency and high greenhouse gas emissions of animal production systems, innovative solutions for conversion of non-edible into edible biomass are urgently required. The present study tested the concept of conversion of non-edible crop residues into edible plant material via heterotrophic plant organ cultures rather than farm animals. Following acid, enzymatic, or microbial hydrolysis, cellulosic waste could be converted into a mixture of monosaccharides, dominated by glucose. The present study characterized the ability of in vitro crop root organ cultures to utilize externally provided sugars for growth, thus converting soluble carbohydrates into edible plant biomass. Results revealed that plant species differ in their heterotrophic capabilities. When grown on sucrose, basil roots were able to convert up to 70% of the supplied carbon into their biomass. Conversion rates on media based on glucose were slightly less efficient compared with those based on sucrose, but still achieved conversion rates of up to 50 %. The efficiency by which cellulosic plant material can be converted into sugars typically lies in the range of 50 – 70 %. Based on this and the results of the present study, root organ cultures would achieve an overall conversion efficiency of 25 – 30 %, far outperforming farm animals and other existing bioreactor-based conversion systems, e.g., based on cell cultures, bacteria, or algae. The present study identified likely opportunities for further improvement of this conversion system. As revealed by the mineral element analysis of the root organ cultures, the Ca and P supply of these plant tissues likely limited their growth performance. Future studies should elucidate reasons for this and develop strategies for increasing the availability of these elements to in vitro root cultures. A comparison of different gelling agents and physical properties of the growth medium revealed only small differences, suggesting that the gelling agent type and strength are not major determinants of culture performance. Liquid cultures did not differ from those on solid media in their ability to utilize sucrose for growth. Further improvement of the conversion efficiency can likely be achieved by culture aeration, e.g. through forced ventilation. Based on the present findings, T-DNA transformation of root organs is not a prerequisite to achieving high biomass conversion rates. In non-transformed, adventitious roots supplied with IBA, the conversion efficiency likely increases with an increasing number of explants added to the culture medium.