Abstract
This study focusses on the design and scale-up of industrial lactic acid production by fermentation of dairy cheese whey permeate based on standard methodological parameters. The aim was to address the shortcomings of standard scale-up methodologies and provide a framework for fermenter scale-up that enables the accurate estimation of energy consumption by suitable selection of turbine and speed for industrial deployment. Moreover, life cycle assessment (LCA) was carried out to identify the potential impacts and possibilities to reduce the operation associated emissions at an early stage. The findings showed that a 3000 times scale-up strategy assuming constant geometric dimensions and specific energy consumption (P/Vw) resulted in lower impeller speed and energy demand. The Rushton turbine blade (RTB) and LightninA315 four-blade hydrofoil (LA315) were found to have the highest and lowest torque output, respectively, at a similar P/Vw of 2.8 kWm−3, with agitation speeds of 1.33 and 2.5 s−1, respectively. RTB demonstrating lower shear damage towards cells (up to 1.33 s−1) was selected because it permits high torque, low-power and acceptable turbulence. The LCA results showed a strong relation between the number of impellers installed and associated emissions suggesting a trade-off between mixing performance and environmental impacts.
Highlights
Whey is a major by-product of cheese and casein manufacturing with a global production of 180 million tonnes per annum
This study focusses on the design and scale-up of industrial lactic acid production by fermentation of dairy cheese whey permeate based on standard methodological parameters
The 100 mL flask was inoculated into 500 mL flasks with enriched media under the same conditions and left until the cells were in a logarithmic growth phase, at which point the cells were transferred into the pilot-scale starter culture tanks
Summary
Whey is a major by-product of cheese and casein manufacturing with a global production of 180 million tonnes per annum. 40% of global whey is disposed of as dairy effluent (Panghal et al 2018) due to its high chemical oxygen demand (COD) (50–80 g L-1) and biological oxygen demand (BOD) (40–60 g L-1) that can lead to adverse environmental impacts (Torres et al 2019). Cheese whey can be valorised to recover high value biochemicals such as proteins through advanced filtration techniques (Deshwal et al 2021; Argenta et al 2021). The leftover permeate still contain the same lactose concentration as cheese whey. It requires effective treatment before discharge into the environment. Fermentation process offers a solution for reducing the organic load to mitigate polluting potential whilst delivering high value biochemicals (Beitel et al 2020)
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