Water-immiscible dissolved oxygen carriers in combination with Pluronic F 68 in bioreactors

The supply and availability of dissolved oxygen (DO) in aerobic bioprocesses is often a limiting factor for the scaling up, improvement and general performance of these bioprocesses. The use of different DO carriers, particularly the use of perfluorocarbons as oxygen carriers, is discussed in this review. It also highlights interactions of microbial cultures with the surfactant, Pluronic F 68. Although oxygen carriers have been used extensively in the medical field, this review only focuses on their use in microbial bioprocess used for the production of high-value bioproducts. The use of water-immiscible compounds in combination with Pluronic F 68 in bioprocesses is discussed with the intention of analysing their combined effect where bioreactor and biomass performance is affected by DO limitations, nutrient starvation, high concentrations of trace element ions, oxidative stress and cell death from mechanical stress

Optimal sulphuric acid production using Acidithiobacillus caldus (DSM 8584): Bioprocess design for application in ion-exchange

An optimised bioprocess was designed for the optimal production of sulphuric acid for application in an isotope recovery ion-exchange process. Firstly, the production of sulphuric acid (H2SO4) was optimised in aerated batch bioreactors using Acidithiobacillus caldus (DSM 8584) using elemental sulphur, achieving H2SO4 concentration of >0.4 to ~0.5 M (0.45 M average) with the following bioprocess parameters: product yield of 3.06 (Yp/s), oxygen uptake rate of 1.35 g/L.day (OUR), 52% sulphur conversion at a rate of 0.83 g/L.day (dS°/dt), achieving a sulphuric acid production rate of 2.76 g/L.day (dP/dt), while the oxidation of elemental sulphur per dissolved oxygen consumed was 0.67 g S°/g O2. Secondly, after 80% (v/v) moisture loss from the recovered biological H2SO4 titres, the acid solution was used for the recovery of nuclear grade lithium 7 (7Li+) from a degraded resin, achieving >80% recovery rate within two bed volumes (60 ml) at an averaged desorption rate K¯ of 0.1829 min -1 and eluent rate of 6.65 ml.min-1 in comparison to the ~60% 7Li+ recovery rate using a commercial grade mineral H2SO4 using similar operational ion-exchange reactor parameters. The designed bioprocess proved to be an effective and environmentally friendly bioprocess for the recovery of valuable metals adsorbed onto ion-exchange resin.Keywords: Acidithiobacillus caldus, sulphuric acid, ion-exchange, desorption, lithium 7 isotop

The Membrane Gradostat Reactor: Secondary metabolite production, bioremediation and commercial potential

This manuscript focuses on the aspect of a membrane gradostat as an entirely different concept compared to submerged hollow fibre modules. The use of membrane bioreactor (MBR) technology is rapidly advancing in the wastewater treatment industries. However, this is not the case in the biopharmaceutical manufacturing industries. The MGR has shown great potential and versatility in terms of industrial applications. It can be used in both wastewater treatment and biopharmaceutical manufacturing using different modes of operation to meet any predetermined process  requirements. The MGR concept uses capillary membranes, which contain microvoids in the substructure to immobilise microbial cells or enzymes, depending on the bioreactor’s application. Operational requirements of the MGR and its commercial potential are discussed from a bioprocess engineering perspective

Product and Microbial Population Kinetics During Balsamic-Styled Vinegar Production

Balsamic-styled vinegar is a nutraceutical product obtained from a two-stage fermentation process of grape must. However, little is known about how fermentation conditions affect growth kinetics, bio-product development, population dynamics and the final product quality. As a result, the current study investigated the effect of fermentation temperature and inoculation strategy on the fermentation dynamics of Balsamic-styled vinegar production. A microbial consortium of non-Saccharomyces yeasts (n = 13) and acetic acid bacteria (n = 5) was tested at various fermentation temperatures (22 °C, 28 °C and a fluctuating temperature regimen). Different inoculation strategies (co-inoculation and sequential inoculation) were investigated, and population dynamics of the product selected due to a rapid fermentation period were confirmed using a 16S and 18S gene sequencing. A higher fermentation temperature (28 °C) and co-inoculation strategy resulted in a shorter fermentation cycle, whilst the desired acetic acid concentration of 60 g/L was achieved within 38 days. 16S and 18S gene sequencing showed that 50.84% of Acetobacter species were abundant at the end of the fermentation cycle, while 40.18% bacteria were unculturable. The study provides a better understanding of how fermentation temperature and inoculation strategy affect the fermentation period, population dynamics and the growth kinetics of the microbial consortium during the production of Balsamic-styled vinegar