Recovery of PHB from Bacterial Cell Matter - Assignment Example

As a measure to minimize the cost of the equipment, a single centrifuge is used to separate the solids from the liquid in three passes to ensure the clarity of the liquid and maximum recovery of the solid part. Careful selection of materials has been done to design the components of the machine, taking care of strength, toughness, resistance to corrosion, and thermal and pressure resistance among other considerations. In addition, there is an instrumentation and control part of the design that will enable optimum control of process parameters to ensure a smooth production process through the production period if the design is implemented.

1.0 Literature Review and Assessment of Alternatives
1.1 General Information

There are various methods used in the recovery of PHB from bacterial cell matter. These include vacuum filtration, ultrafiltration, microfiltration, candle filtration, press filtration, flotation, and centrifugation. Several of these recovery processes have been investigated in order to come up with the most economic method to isolate and purify PHB. It is used in the separation of cells and particulate materials after the fermentation stage. Centrifugation is the most ideal method that is normally used to separate PHB from the medium (Harker, et al., 2013). Following this, PHB extraction and purification can be achieved using a number of ways. The most existing methods for the recovery of PHB involve using organic solvents, such as chloroform and acetone, and the use of a hypochlorite, such as sodium hypochlorite.

Centrifuges use a centrifugal force generated by high-speed rotations to separate solid suspensions from liquids. In the processing of PHB, centrifuges are used to recover and clarify the biomaterial from a mixture of PHB and cell matter (Pohorecki, et al., 2010). Centrifuges can either be sedimentation units or filtration units. In a sedimentation centrifugal unit, the separation of substances relies on the difference in their densities. As the slurry is fed into the spinning centrifuge, an annulus is formed next to the bowl wall and the liquid is picked up by a skimmer (Van Wegen, et al., 1998). The solid material is removed from the centrifuge quite often to enable a continuous separation process. Filtration centrifuges, on the other hand, filter the material by use of a rotating basket with a filter medium and a centrifugal rotational force expels the liquid via the filter (Tarleton & Wakeman, 2011). Large-scale centrifugation equipment is made of disk-stack and decanter centrifuges. The disk-stack centrifuges run at higher speeds and remove lighter biomass material. When coagulant agents are available, the decanter centrifuge improves performance. Centrifugation does not need filter aid, which counts as one of its most significant advantages against rotary vacuum filtration. To recover the PHB biomaterial, the paste obtained is normally washed and returned to the centrifuge for another pass.

1.2 Extraction of PHB using Centrifuges

Extraction of PHB from bacterial cell matter plays a critical role in the optimization of the production of the polymer. This means that a good extraction method must lead to the maximum achievable recovery rate of PHB at a lower cost which will make the production of the polymer profitable. One of the main cost factors of PHB production is the process of recovering the polymer (Rousseau, 1987). In addition, a reasonably high rate of recovery and purity using inexpensive and environmentally friendly equipment with a few separation steps that are easy to apply is vital to achieving an economically and environmentally feasible process.