Upscale fermenter design for lactic acid production from cheese whey permeate focusing on impeller selection and energy optimization.

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/V w ) 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/V w 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. Supplementary Information: The online version contains supplementary material available at 10.1007/s13197-021-05239-6.

Techno-economic implications of improved high gravity corn mash fermentation.

The performance of Saccharomyces cerevisiae MBG3964, a strain able to tolerate >18% v/v ethanol, was compared to leading industrial ethanol strain, Fermentis Ethanol Red, under high gravity corn mash fermentation conditions. Compared to the industrial ethanol strain, MBG3964 gave increased alcohol yield (140g L(-1) vs. 126g L(-1)), lower residual sugar (4g L(-1) vs. 32g L(-1)), and lower glycerol (11g L(-1) vs. 12g L(-1)). After 72h fermentation, MBG3964 showed about 40% viability, whereas the control yeast was only about 3% viable. Based on modelling, the higher ethanol tolerant yeast could increase the profitability of a corn-ethanol plant and help it remain viable through higher production, lower unit heating requirements and extra throughput. A typical 50M gal y(-1) dry mill ethanol plant that sells dried distiller's grain could potentially increase its profit by nearly $US3.4M y(-1) due solely to the extra yield, and potentially another $US4.1M y(-1) if extra throughput is possible.