Development of a Water Activity Control and Reaction Monitoring System for Acidolysis and Transesterification Reactions using Immobilized Lipases in a Rotating Bed Reactor

Abstract

Controlled water activity in an enzymatic reaction can influence enzyme activity and productivity. A small layer of water around an enzyme gives it a required flexibility to catalyze reactions at a higher rate in contrast with the one that is dry (Adlercreutz, Dicko, Larsson, & Månsson, 2017). The hypothesis of this research project is that the product yield and productivity of acidolysis and transesterification reactions will be increased with the controlled water activity.
The acidolysis reaction is performed in two steps, where the first one is hydrolysis of the ester followed by reversed hydrolysis creating the new ester with the desired acid. Higher water activity promotes hydrolysis and vice versa for the reversed hydrolysis.
In this degree project a modified SpinChem rotating bed reactor was developed for the acidolysis and transesterification reactions. The reactor was equipped with an automatic water activity control system which was designed in the laboratory. The automatic water activity control system was made from two sub-systems. A nitrogen sparging and a relative humidity sensing system. The latter was kept in the headspace of the reactor while the nitrogen sparger was installed in the bottom of the reactor and was connected to dry and wet nitrogen. An Arduino UNO R3 micro-controller was used for communication between mentioned systems. The automatic water activity control system was designed in a way where a 3-way valve was switched between the dry and wet nitrogen source based on the setpoint of the humidity ant the actual value in the reactor, and where the flow of nitrogen gas was regulated by the Aalborg thermal mass flow controller based on the difference between the setpoint and the actual relative humidity.
A software for the communication between the sub-systems was written using C++ programming language using Notepad++ free source code editor. The code was later imported in the Arduino integrated development environment (IDE) and transferred to the micro-controller. The code was written in the way were the micro-controller was able change the parameters of the gas flow and switch the 3-way valve between the dry or wet nitrogen based on the data received from the relative humidity sensor.
The automatically controlled relative humidity system was able to maintain water activity in the reactor with the standard deviation ranging from 0.015 to 0.058 aw units when going from 0.1 to 1.00 aw respectively.
Automatically controlled water activity system was later used in a transesterification and acidolysis reactions. Different water activities were maintained in the reactor while the conversion of a substrates was tracked with the gas chromatography. Results suggested that the water activity has a significant influence on the enzyme activity during transesterification reaction. In some cases, the activity of an enzyme in the reactor was increased several times by increasing the water activity. During acidolysis reaction the water activity had of a great importance on final substrate conversion and reaction rate. At the water activity of 0.9, 2.5 times more product was converted after 5 hours, compared to the water activity of 0.25. This shows that there is a great importance of controlling the water activity of enzymatic processes.

Popular Abstract

Enzymes are biomolecules found in all organisms on Earth. In the human body, these molecules perform different kinds of reactions, for example enzymes can degrade starch from food to glucose or to degrade alcohol, which is toxic, to less toxic compounds. As soon as the working principle of enzymes was understood, they were employed in various industries. The most common industry, where enzymes are used, is the food industry. In the food industry enzymes are used to produce among other things, margarine and cocoa butter substitutes from cheap oils. In other words, cheap substrates are used to produce more valuable products with the help of enzymes.
In the industrial applications enzymes are stored in big tanks, called reactors. These reactors are big vessels, usually made from metal. A human body can be understood as the reactor, where millions of enzymes are performing various conversions.
Enzymes, naturally, are working in aqueous media, meaning that water is very important for enzymes to operate optimally. In order to employ enzymes in the industry the amount of water in the reactor should be considered. The amount of water in the industrial reactor is very important, the same way as it is important in the human body, and it must be controlled in order to keep enzymes active. The same goes for temperature, pH and other factors, that could influence how good the enzyme will perform.
Every organism has its own optimum environment in order to feel and operate well. The same applies for enzymes. If the amount of water, substrate and product is controlled and kept at the optimum level, the enzyme will operate at its highest rate, meaning that more product will be produced in shorter period. That idea was the main for this project, to find optimum conditions for enzymes to operate in reactors. In order to find and maintain optimum conditions for enzymatic reactions a system which controls water amount in the reactor was made. This system was able to keep the optimum conditions for the enzyme in the reactor, thus increasing the amount of final product.

• author: Gladkauskas, Eimantas
• supervisor: Carl Grey
• organization: Biotechnology (MSc); Biotechnology (M.Sc.Eng.)
• course: KBTM01 20191
• year: 2019
• type: H2 - Master's Degree (Two Years)
• subject: Technology and Engineering
• keywords: Enzyme, Enzymes, Immobilized enzyme, bioreactor, rotating bed reactor, acidolysis, transesterification, arduino, water activity, thermodynamic water activity, Enzyme activity, automatic reaction tracking, reaction tracking, biotechnology, electrical engineering, relative humidity, spinchem, enzymatic synthesis, water activity control, process automation, lipases, lipase, bioteknik
• language: English
• id: 8986366
• date added to LUP: 2019-07-04 13:55:38
• date last changed: 2019-07-04 13:55:38