Bioprocess Engineering

Bioprocess Engineering - BioConversion & Separation Technologies

Introduction

The general aim of the research is the investigation of the effect of process variables on the performance of bioreactors and separation processes, and how this information can be utilised on a process scale. Another objective of the research is the education of students in bioprocess engineering.

 Lactic Acid Production from Whey Permeate by Fermentation

Whey permeate consists mainly of lactose in solution with ash and soluble nitrogen, and is produced as a byproduct of WPC production. There is continuing interest in ways of utilising this byproduct. One alternative is the production by fermentation of biochemicals, such as lactic acid. There is a potential future market for lactic acid biodegradable plastics which would greatly increase the production of lactic acid world-wide. However, lactic acid producers are mainly looking at producing the lactic acid from sucrose and dextrose-based media. Thus, there exists a challenge in bridging the gap between whey permeate surpluses and lactic acid production.
Fermentation of whey permeate requires a nutrient supplement. Addition of nutrient supplement is an extra fermentation cost, and also adds to the level of residual impurities which have to be removed after fermentation by purification steps. Purification can be the most costly part of biochemical production. Therefore, the research is focused on evaluating how little nutrient supplement is required while still achieving a high level of lactose conversion to lactate and reasonable fermentation time. Ash content is another major impurity in whey permeate and thus the fermentation of regular and de-mineralised whey permeates are being investigated.

 Whey Protein Fractionation: Effect of Precipitation Reactor Variables

Proteins can be fractionated by precipitating out one or more of the proteins and separating the precipitates in a centrifuge. Shearing of protein precipitates in pumps, pipes and centrifuges can lead to break-up of the precipitate particles and reduction in particle size which makes the particles more difficult to separate in centrifuges.
The focus of this work is investigating how agitator shear during precipitation in a stirred tank and precipitation time affect the particle size distribution, fractal dimension and the strength of the precipitate particles produced; and how this affects subsequent processing for example in pumps and centrifuges. The basic concept is the stronger the precipitate particles produced during precipitation, the less likely they are to be broken down, and thus the easier they will be to separate. The system studied is the fractionation of the whey proteins a -lactalbumin and b -lactoglobulin.

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