Protein manufacturing
The UniProtein production process is aerobic with natural gas as the carbon and energy source. Air or pure oxygen is used for an oxygenation fermentation process and ammonia is used as the nitrogen source. In addition to these substrates the UniProtein culture requires water, phosphate and several minerals including magnesium, calcium, potassium, iron, copper, zinc, manganese, nickel, cobalt and molybdenum. Sodium hydroxide and sulphuric acid are used for pH regulation. All chemicals are of food-grade quality. Phosphate is supplied as phosphoric acid, the minerals as sulphates, chlorides or nitrates. The pH is regulated to 6.5+/-0.3, and the temperature is kept at 45°C+/-2°C.
UniProtein is produced in a continuous fermentation. A U-loop fermentor with static mixers is used. The U-loop fermentor gives a high utilisation of the gases, which are carried through the loop by the liquid flow in almost plug-flow mode. Gases are introduced at the start of the loop and stay in well-mixed contact with the liquid until they are separated in the headspace at the end of the loop.
A high biomass concentration with a high metabolic activity throughout the fermentor ensures that methane and oxygen are rapidly utilised as soon as they are dissolved in the fermentation liquid. The overall gas utilisation in the loop fermentor can exceed 90%.
After each campaign of four to five weeks' continuous operation, the fermentation system is cleaned with hot sodium hydroxide followed by a short treatment with a dilute nitric acid solution and sterilisation with steam at 120°C for one hour. The fermentor is filled with water, which has been heat sterilised at 130°C for ten seconds. Gases and solutions of minerals, ammonia and phosphoric acid are all sterile when fed into the fermentor. Addition of the different nutrients is regulated according to their consumption. The control system includes online measurements of headspace gases and the ammonium concentration in the medium. The feeding of mineral nutrient solutions is programmed according to detailed knowledge of the stoichiometric requirements and UniProtein culture for the different minerals.
The continuous fermentation is operated with 2-3% biomass (dry matter) and a dilution rate of 0.20 0.25 h-1. The biomass of the harvest is concentrated to over 15% by centrifugation and then to approximately 30% by ultra-filtration (UF). The concentrated biomass is quickly heated to 140°C in a UHT (ultra-high temperature) unit in order to obtain a sterile product followed by a quick cooling to approx. 70°C. In the process the biomass is inactivated, and the cell undergoes lysis so that the protein becomes more accessible. Finally, the UHT-treated biomass is dried in a spray dryer with an integrated fluid bed. This gives a non-dusty agglomerated product.
In order to minimise the use of process water and the amount of waste water, process water from the centrifuges and ultra-filtration is returned to the fermentor after a short heat treatment.
The product is routinely examined for microbial contamination, water content and chemical composition. Tests have shown that the UHT treatment kills all the bacteria used in the production of UniProtein. Spray drying is the last step in the production of UniProtein. It undergoes no other technical processes of preparation before use.
Fermentation
Most living organisms are capable of transforming carbon, nitrate and minerals of organic or inorganic origin into new cell mass. Carbon is the ”skeleton” in the newly formed cells. It also delivers energy for the multiple biosynthetic processes in the organism. Nitrogen – often as ammonia (NH3) – is built into the proteins of the organism via amino acids, and the biomass contains up to 70% protein.
The so-called methylotrophs are capable of living and growing on these simple substrates. In contrast to other organisms – that all require sugar as the primary source of carbon – they are capable of growing on methane (CH4) or methanol (CH3OH), i.e. a carbon source containing only one carbon atom.
UniProtein is manufactured by adding methanol to a culture of methylotrophs along with ammonia or nitrates and a range of simple minerals. It is an aerobic process, and the oxygen transforms part of the carbon into carbon dioxide through respiration, a process that creates a large energy surplus used by the organism for growth.
The process
Summing up, the substrates for making UniProtein are: A nitrogen source (methane or methanol), natural gas or methanol, minerals and oxygen.
The main requirements for the process design are clear: A large container is needed – the fermentor – where the bacteria are kept. To this container oxygen – potentially as air – and gas or methanol are fed. Another liquid feed contains the nitrogen source and minerals. From the container newly formed biomass is continously harvested together with the aqueous solution containing the remains of the substrates. The biomass can then be separated in a centrifuge, and the liquid returns to the fermentor.
Further treatment of the biomass is simple: Remaining liquid is removed by filtration (UF), and the biomass is dried in a spray drier and then stored in sacks or silos.
The fermentor
The design of the fermentor is one of the more important aspects of the process. In traditional stirred fermentors there are problems with achieving sufficiently small bubbles (large surface area of the gas), and there is a large energy waste due to inefficient stirring of the bulk liquid. Furthermore there are problems with cooling when upscaling.
• The fermentor that is to be used in the UniBio factory is based on the patented U-loop fermentor, developed in cooperation with DTU. In the U-loop design we have achieved a much larger surface area, and mechanical stirring is no longer needed. A 50 m3 nozzle-loop fermentor and a 20 m3 U-loop fermentor have been built and tested by scientists from DTU. 
Apart from being much more effective – 4.0 kg/m3/h against <1.8 kg/m3/h – than traditional fermentors, there is about 30% energy saving in the U-loop fermentor.
U-loop fermentor
1. Degassing unit
2. Continuous harvest of biomass
3. CO2 outlet
4. Two-fase nozzle, where fluid from the fermentor is mixed with air and then reinjected into the fermentor to achieve small bubbles.
5. Nozzle pump
6. Injections of medium
7. Cooling
8. Propeller pump for moving the fluid through the loop
9. Engine for pump
10. Static mixers. Prevent bubbles from merging while moving through the loop.