Grantee Research Project Results
Final Report: Biopolymers for Sustainable Agricultural Solutions
EPA Grant Number: SU836792Title: Biopolymers for Sustainable Agricultural Solutions
Investigators: Sengor, S. Sevinc
Institution: Southern Methodist University
EPA Project Officer: Page, Angela
Phase: I
Project Period: September 1, 2016 through August 31, 2017
Project Amount: $15,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet (2016) RFA Text | Recipients Lists
Research Category: Sustainable and Healthy Communities , P3 Awards , P3 Challenge Area - Chemical Safety
Objective:
The objective of this study is to investigate the innovative use of a biopolymer compound, produced from Rhizobium tropici sp., on the enhanced germination rate of tomato plants, and its impact on enhanced nutrient adsorption of the plants, using hydroponics experiments. This is extremely crucial from a sustainability of materials and chemistry standpoint, as it will provide a highly effective solution for reducing nutrient runoff as well as nutrient leaching in urban agricultural systems. Urban agriculture plays an important role in community development and in addressing issues related to healthy food access and food security in disadvantaged urban communities. In the United States, urban agriculture has historically occurred on a smaller scale, often in the form of community gardens; whereas, recently it has been scaled up significantly mainly to make the food production system more sustainable, resilient, and socially just (Wortman and Lovell, 2013). However, urban agriculture efforts continue to face challenges, especially when it comes to soil contamination, water availability and contamination, and nutrient runoff. Furthermore, questions related to the economic viability of urban agricultural systems are creating the need for more research about urban farming productivity and profitability.
Conserving water resources also is critical, where diversification of water sources could reduce the pressure on municipal sources for water. In addition to the recycled water use, harvesting rainwater from rooftops and other impervious surfaces has becoming a popular source for irrigation in urban areas. However, when harvested rainwater is to be used to irrigate food crops, a major concern is the potential contamination coming from the roof runoff, including heavy metals, bacteria, and other microbial pathogens that could cause various illnesses when consumed through edible portions of the plants. The project proposed here is focused on addressing these problems through the innovative use of a biopolymer material (obtained from Rhizobium tropici sp.), which will be amended in plant samples to determine its efficiency in retaining heavy metals, and enhancing nutrient absorption. This will result in reducing the quantity of fertilizer needed by the plants.
Rhizobium tropici are symbiotic bacteria that nodulate plant roots using plant sugars to produce a biopolymer film. The functions of this film include surface adhesion, water retention, and nutrient accumulation. A variety of bacterial species can produce these substances that participate in the formation of microbial aggregates (Geesey, 1982), whether the bacteria is grown in suspended cultures or in biofilms. The microbial biofilm or the floc that is formed consists of bacterial cells enveloped by a matrix of large polymeric molecules, named extracellular polymeric substances (EPS). As the name implies, EPS are located at or outside the cell surface. Their composition may be controlled by a variety of different processes, including active secretion, shedding of cell surface material, cell lysis, and adsorption from the environment (Wingender, et al., 1999; Laspidou and Rittmann, 2002). Among the functions of the EPS matrix are adhesion to surfaces, aggregation of bacterial cells in flocs and biofilms, stabilization of the biofilm structure, formation of a protective barrier that provides resistance to biocides or other harmful effects, retention of water, sorption of exogenous organic compounds for the accumulation of nutrients from the environment, and accumulation of enzymatic activities, (e.g., digestion of exogenous macromolecules for nutrient acquisition) (Laspidou and Rittmann, 2002).
An important function of the extracellular protein is that they can trap, bind, and concentrate organic materials in close proximity to the cells. The extracellular enzymes, as they are localized at or outside the cell surface, can hydrolyze the sorbed organic matter. This facilitates the efficient uptake of hydrolysis products by reducing diffusion loss of products to the surrounding water (Hoffman and Decho, 1999; Wingender, et al., 1999; Laspidou and Rittmann, 2002).Various bacterial species are reported to synthesize and excrete EPS (Castellane and Lemos, 2007; Monteiro, et al., 2012; Mota, et al., 2013; Radchenkova, et al., 2013; Silvi, et al., 2013). After being transported to the extracellular space, EPS exists as either soluble or insoluble polymers and are either excreted into the environment as slime or they are loosely attached to the cell surface. Bacterial production of EPS has been studied and recognized as a cohesive force facilitating resistance against erosion in sediments (Droppe, 2009; Gerbersdorf, et al., 2008a, 2008b; Larson, et al., 2012) In the marine environments, it has been recognized as an important alternate route for organic carbon cycling (Bhaskar and Bhosle, 2005). EPS also has been demonstrated to promote soil adhesion for several cyanobacteria in arid environments (Hu, et al., 2003).
Among the bacteria that produce EPS, Rhizobia sp., has been reported to excrete large amounts of polysaccharides into the rhizosphere and, when grown in pure cultures (Noel, 2009), produce abundant amounts of EPS, causing an increase in viscosity (Castellane, et al., 2014). Due to the adhesive, water retention, and protective biofilm formation characteristics of the EPS produced by R. tropici, it has been investigated as a potential soil engineering agent (Larson, et al., 2012). The main characteristics of this biopolymer include:
- Surface adhesion
- Water retention
- Nutrient accumulation in the soils
As these biopolymer films produced by Rhizobia sp., have been tested and proved to be efficient especially with regards to surface adhesion, water retention, and improved germination characteristics, these results warrant investigation of the impact of biopolymer potential to (i) enhance water retention in the matrix, (ii) improve the germination characteristics in the matrix, and (iii) enhance the retainment of heavy metals in the hydroponic units. We will investigate the impact of the biopolymer potential to increase the rate of germination of the tomato plants and to enhance the nutrient uptake by the plants.
Summary/Accomplishments (Outputs/Outcomes):
The Team has been undertaking experiments that are carried out in a controlled laboratory environment using tomato plants, with three simultaneous objectives. The first is to study the impact of the application of biopolymer compound, produced from Rhizobium tropici sp., on the growth of the tomato plants, to be measured based on the quantity and amount of tomatoes harvested. Second, the study also is designed to measure the sugar and nutrient content of the fruits harvested to compare the nutritional attributes of the treatment and control groups. Third, the ongoing experiments also study the quality of the water circulating in the hydroponic system, to test the degree to which ammonium and other nutrients are removed from the water in the treatment and control groups. Our results show about 50% heavier tomatoes with higher sugar content when 0.5% of biopolymer concentrate was used in the hydroponic system. Water quality analysis showed higher nutrient (nitrate and phosphorous) absorption by the biopolymer treated unit. Our root scanning analysis showed larger root systems for biopolymer treated plants, indicating the potential for increased yield, increased food quality, reduced fertilizer needs, and thus the economic effect of biopolymers for smallest footprint in urban farming.
Conclusions:
The Phase I project results discussed above warrant further investigation of the innovative application of the polymer for a variety of crops for reduced fertilizer use with optimum crop efficiency, which is the main focus of this project. Rhizobium tropici are symbiotic bacteria that nodulate plant roots using plant sugars to produce a biopolymer film. The bacteria can be stimulated to produce large quantities of this biopolymer that can be concentrated and dried into a soil amendment. Biopolymer compounds produced by Rhizobia sp. also have been previously tested and proved to be efficient especially with regards to (i) enhanced water retention in the soils, and (ii) enhanced microbial nutrient uptake efficiency in the soils (Larsen, et al., 2012), which are the main factors affecting profitability in urban agriculture. A participatory social science research project was launched in June 2015, to study the households in Jubilee Park in South Dallas, where the Hunt Institute also installed a small educational aquaponic system. The research has been IRB approved and tested on a small group of respondents. The full-scale baseline survey will commence in January 2016.
Supplemental Keywords:
Biopolymer concentrate, urban agriculture, sustainability practice, tomato plants, hydroponicsThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.