GrassRoots

Bioreactor for Indigestible Cellulose Conversion to Edible Glucose to Combat Malnutrition and a Case study review of hunger in burundi

in collaboration with Akhil surapaneni, catherine schult, Chris vangundy, natalie bolton, patricia dasilva, peter tang

Problem Statement

Burundi is a small country in central Africa and of Burundi’s 10.88 million people, over half are chronically malnourished. Malnutrition manifests in different ways,  one of which is marasmus, a condition defined by an overall deficiency of calories. Calories are mainly assimilated into the body through foods containing carbohydrates and fats. However, 58% of Burundi’s population cannot access enough of these necessary calories. This disheartening statistic is linked in large part to the Burundian Civil War and consequential food insecurity, high poverty rate, and high inflation. Despite the country’s return to peace in 2005, as of 2014, Burundi’s Global Hunger Index (GHI) remains one of the largest in the world.

As a result of a starch-heavy diet, the average Burundian consumes about 10 g less protein per day than the average sub-Saharan African. Considering that 37.5% of their expenditures are on starch products, whereas animal protein products and medical expenses are valued at 9.2% and 5.8%, respectively, a large caloric supplement in starches should benefit Burundian families allowing for allocation of greater percentages of their total monthly expenditures on other necessities, such as protein or medical expenses.

Presently, solutions tend to come in two primary flavors: short term food aid and long term policy change and economic reform. Short term food aid comes mainly from large Western non-profit organizations, including USAID, which spent upwards of $20 million USD in 2015 delivering more than 6,500 metric tons of food in Burundi alone. This is an extremely expensive approach to malnutrition that only works as a “band-aid,” addressing a complex problem with a short term and temporary solution. Policy changes and economic reform occur slowly, with many international organizations publishing studies and recommending solutions to the economic (and thereby indirectly hunger) problems of Burundi and other impoverished countries.

That is not to say that an engineering solution to malnourishment has never been proposed. GRAIN, a small nonprofit hunger organization, discusses the use of rice genetically enriched in Vitamin A as a method of increasing nutrition to malnourished areas. Additionally, the work of Dr. Percival Zhang at the University of Virginia has engineered state of the art techniques in cellulase enzyme hydrolysis and its potential as a source of both biofuel and starch. Although both solutions outline a viable source of nutrient production, they fail to address the difficulties associated with transporting large quantities of nutrients across international borders and through underdeveloped rural terrain. Current solutions to malnutrition do not effectively integrate into low resource settings because they are not sustainable and immediate. Therefore, a self-sustaining device to provide food energy to malnourished populations is needed. This will allow communities that are unable to reliably purchase food to have access to a continuous caloric supply with little marginal cost. 

Work Done and Proposed Solution 

In order to create a self-sustaining device that is effective and easily integrated into a low-resource environment, many design criteria were considered. Our device must convert indigestible cellulose into digestible monosaccharides including glucose. It also must run on net-zero energy to be independent of typically unreliable electrical power in developing countries. The machine should be inexpensive relative to money spent on Burundian food aid by USAID, costing no more than $100,159, efficient, converting glucose to cellulose with at least 70% efficiency, reliable, requiring no maintenance during its life expectancy of at least 5 years, and autonomous, requiring 0 user interactions (aside from inputting plant matter) to convert input to digestible output for ease of use.

The agricultural economy of Burundi was researched to determine the most sustainable source of plant matter input. Burundi’s largest export is coffee, accounting for 51% of the country’s total exports. Appropriately, 2.3% (60,000 hectares) of Burundi’s total land area is utilized for coffee cultivation, and 58% of Burundian households depend on coffee farming as a source of income. However, coffee-processing is wasteful. To obtain the final coffee bean, the coffee cherry must be shredded of its exterior skin and pulp, a sugar and pectin-rich cushion for the coffee beans. Therefore, 43% of the cherry’s original volume is thrown away, polluting water sources as a result of its biochemical decomposition. In fact, research has demonstrated that for every one kg of dried coffee beans, about 3.3 kg of fresh pulp and mucilage are produced, with a chemical oxygen demand equivalent to that of the sewage generated in 1 year by 1.2 million people. The environmental effects from coffee processing are severe enough to be addressed in the “Rapid Strategic Environmental Assessment of Coffee Sector Reform in Burundi.” Therefore, to approach the design of our bioreactor from both a humanitarian and environmental standpoint, specifications of components have been modified to accommodate coffee pulp as our primary plant matter input.

Our solution for a self-sustaining device is a bioreactor that has processes compartmentalized into the following components: plant storage, grinder, liquid hot water treatment, enzyme reaction, ultrafiltration, and product dehydrator. The bioreactor has a set of stages through which the plant matter input flows (Figure 1). The biomass first enters through a grinder where it is physically broken down. It is then treated with liquid hot water to increase cellulose accessibility within the plant cells. From there it undergoes an enzymatic reaction that utilizes both an immobilized enzyme and a continuous recycled flow system to optimize the conversion of cellulose into glucose. Final output consists of dehydrated glucose and plant product, ready for consumption. The bioreactor will be powered by an array of photovoltaic panels that gathers solar energy, a battery that stores the energy, and a DC to AC converter that delivers energy to the components. Through initial calculations, this novel method allows humans to harness food energy stored in any cellulosic matter for about $65,900 less than what is currently spent by USAID. Furthermore, additional calories are provided through a process that repurposes an otherwise wasted agricultural byproduct, runs solely on solar energy and recycles all water used to ultimately create a sustainable bioengineering solution to world hunger.

Our bioreactor attacks the root of the problem. It serves as a source of food production that taps into a source of previously inaccessible nutrient while also remaining physically proximal to the communities it will be helping. We expand upon Dr. Zhang’s work in optimizing the cellulase enzyme to convert cellulose into glucose instead of starch, while simultaneously dealing with the more complex issue of transporting nutrients into malnourished areas by locating the machine in the communities themselves.

Outcome and Future Work

Future work involves optimizing production of the glucose-based food output and expanding on the device’s potential applications. Key considerations going forward include: enzyme optimization, water recycling system validation, and expansion of the  application of the bioreactor to other situations.

The enzyme solution is currently under neutral water pH conditions of 7.0. While this pH allows the enzyme to function, it is at the upper limit of the enzyme’s functional pH range. The optimal pH generally lies between 4.0 and 5.0. A key step going forward is to design a system to sustainably maintain a pH within this range to improve our overall reaction conversion. In addition, a mechanism to remove cellobiose, another inhibitor of the cellulose to glucose reaction should be implemented.

As another technical hurdle, the water recycling system must be validated in order to account for the vapor pressure gradients present throughout the system. The water present in the product is dehydrated and the vapor would ideally rise into the water tank. However, there may be a higher water vapor pressure within the tank, impeding water vapor flow. The equilibrium point would need to be established in order to move forward with the design or make modifications to the product and water chambers.

In addition to serving chronically malnourished communities, this machine has the potential to aid regions affected by natural disasters. After further optimization,  a surplus of food can be stored for emergency situations. For instance, in Burundi, the frequency of meals/day changes drastically based on the time of year. For example, during harvest season, children and adults average 2.2 and 1.9 meals/day, respectively. However, during lean season, those numbers decrease to 1.7 and 1.2.9 Because our product is a dehydrated glucose substance, this will allow for easy storage, which may help if there is ever limited access to food.

In regards to accomplishments the bioreactor is not only functionally viable but also cost effective. To determine the value of the device, price of manufacture was compared to the “worth” of the device in terms of the calories distributed per dollar spent by USAID. The estimated value in USAID dollars amounts to $100,159.08 while the cost to manufacture is  $34,599.37. This proves that our device is a cost-effective method of providing calories compared to food relief programs, the current solutions combatting the global malnutrition crisis.

Awards

Rice University Owl Open Student Startup Competition 3rd Place (2016)

Press

BIOE undergrads win OWL Open cash prize (Rice University)