Bacterial cellulose production Mini Factory
Our hardware is a model of minimized automatic production line of bacteria cellulose. To illustrate our manufacturing application, we designed a simulation production hardware using AutoCAD and 3D printing after consulting engineering knowledge and actual applications.
In order to simulate the actual fermentation process, we investigated paper mills to clarify how waste paper pulp was treated before production. The conventional way of paper recycling is listed below:
When waste paper is collected in factories, it will be firstly mixed with water to be grinded into pulp. And then adding acid or alkali can break the internal structure of lignocellulose which makes it soluble. After that, pH is adjusted to 5~7 and cellulase is added to hydrolyze cellulose. To avoid contamination of bacteria and fungi, bactericides and fungicides are added into the solution. During the process of paper recycling, a numerous number of power and water is consumed. So, combined with our project, we designed our factory based on common production line, with simple modifications to serve us better.
After investigation, we set 7% of the whole waste paper pulps yearly used by paper mills as our large-scale factory yield, we designed a 200m3 fermenter to produce bacterial cellulose. it is nearly impossible to test the productivity of a fermenter so big, so we designed a 500 L volume fermenter as a pilot scale to simulate our process.
By modelling data, we estimated that the suitable cellulose concentration was 20 g/L~40 g/L. Because the volume of a liquid fermenter is generally 60%~70% of its whole volume, cellulose concentration is commonly 20g/L~40g/L in a 350L scale, we designed a 25L jar to store waste paper pulps as our initial raw materials.
In order to satisfy the requirement of culturing E.coli and at the same time not destroying the structure of our product bacterial cellulose, we used an airlift fermenter to minimize shearing damages, which can provide enough DO and a really low shear force, also it is under appropriate costs.The inoculum is generally 10% of the fermentation volume and for 350L fluid, we designed two tanks of different seed ranks(seed is the original strain). For 10% inoculum, the first seed tank is 10 L and the second seed tank is of 50L volume. Besides, we designed several jars for acid, alkali, supplementary sugar and lactose, and the size of each is about 25L.
Further more, our simulation model is equipped with automatic online parameter detection and modularized production line, which is an obvious trend of future biological plant.
Figure 1.Section view of our mini factory
With the help of our State Key Laboratory of Bioreactor Engineering, we applied AutoCAD to draw a 3D model, including a 500L airlift bioreactor, a primary and a secondary seed tank, the fed-batch pots and other supplementary parts, which can be better demonstrated by 3D printing.
Figure 2. Dynamic representation of our mini factory
Our engineered bacteria paper transformer is firstly cultured in primary and secondary seed tanks and then in the airlift fermenter. This is of great challenges and innovations in this area and we provided a good example for making waste to treasure at the same time protecting our environment.
Based on this model, we can later magnify the production scale with increased size and parallel number of bioreactors, which may come true with the further cooperation with downstream device companies. The newly designed bioreactor system we built can perfectly serve to our purpose—transfer lignocellulose to bacterial cellulose.
DO: dissolved oxygen, further explanation