OVERVIEW

Bringing Oviita to the community

The aim of our project is to supply communities experiencing vitamin A deficiency with our product, Oviita, to provide them with a sustainable source of nutrients. For this to happen we will need to culture the yeast at the local community level. Therefore, we needed to develop a bioreactor capable of accomplishing this task in suboptimal conditions while also being sensitive to the available resources in these areas.

Lab Adaptable Bioreactor:

PHYSICAL DESIGN

To produce accurate models and projections, we will need accurate data. At the same time, we need our Lab Adaptable Bioreactor to resemble conditions in the field and therefore should be of relatively similar scale. Given our initial estimations, a 40L bucket should be able to produce enough yeast for a small group of people and therefore would suffice. Removing as much yeast with as little water possible was a significant challenge to overcome. Yeast are single celled fungi ranging between fungi, 5~10 μm in size. Centrifugal separation would leave us with too much water and typical micron filters would get clogged and become quickly ineffective. Fortunately, we found a stainless steel, 1 micron, 4 layer mesh filter that won’t clog as easily and can be cleaned in an autoclave.

ELECTRICAL DESIGN

The data we needed to collect is the growth conditions against diffused oxygenation levels, pH, temperature, the corresponding growth rates, settling rates and anything else that may require design considerations.

To achieve this we have the Gravity: Analog Dissolved Oxygen Sensor for determining the oxygenation rates in the solution because the yeast is an obligate aerobe meaning it requires oxygen to grow. Literature has shown substantial growth with 9L/min of air being pumped into the solution and therefore we are using a commercial air pump for aquariums that is capable of delivering a maximum 50L/min of air (Braga, 2015, 55-62). From that, we will be able to determine the minimal amount of oxygenation needed for growth and find a range of values to be able to predict the growth for that specific range.

To monitor pH, we are using the Gravity: Analog pH Meter Pro. This way we can continuously monitor the pH as it might change with cellular respiration. Our concern is that the yeast will convert the oxygen into CO2 and that CO2 in the solution will lower the pH to a point where the yeast will no longer be able to sustain life. Fortunately, our yeast can thrive at a pH of 4.5 so some acidification is ok. (Timoumi, 2016)

In order to maintain or simulate the temperatures or temperature fluctuations of the locations we intend on distributing our yeast, the bioreactor will have an aquarium heating element and a DS18B20 digital thermometer.

Each of the components is controlled with an Arduino inside a 3D printed box with all of the data being saved to the Geekstory micro SD module as comma separated values in a text file. This text file can then be used to create a graph using the data. In addition, a DS3231 time module will timestamp the data to ensure an accurate interpretation of the data.

SAFETY

Field Adaptable Bioreactor:

A general design for a field reactor includes two tanks; one tank will act as the main culturing tank and the second tank will be the collection tank. Once the main tank has reached the desired levels of yeast production, users will drain 75% of the solution into the collection tank. In the collection tank, the yeast will have time to settle to the bottom. A drain located just above the height of the settled yeast can then drain most of the water leaving the yeast behind. To minimize the modifications/parts required, a simple siphon can be constructed. (see photos) The remaining water could then be evaporated by placing a fire under the collection container making the yeast easier to collect, store and consume. The fire would also be able to sanitize the collection tank to ensure nothing harmful begins to culture.