Growth of fungi and yeasts in food production waste streams: a feasibility study

Food production produces nutrient-rich waste streams which, depending on local legislation, are either sent to wastewater treatment plants or discharged into the environment. In addition to causing environmental harm in the second instance, valuable nutrients are lost. A more circular approach would be to reuse these waste streams. Fungi and yeasts are ideal candidates as they require lots of organic carbon (which is especially high in food production waste streams) for growth, with the potential for producing value-added biomass. Here, we tested the metabolic activity and possible growth of seven fungi and three yeasts in five different food production waste streams. Initial tests were done to find the most promising waste streams for growth and these were chosen for further study. All species were then cultured in these waste streams and oxygen uptake was measured to gauge metabolic activity which we used as a proxy for growth rate. Pelletization's effect on metabolic rates was tested on the most pellet-forming species, by adding agar to inhibit pellet formation. The most promising waste stream for yeast/fungal growth was cheese whey (Whey). Pellet inhibition (i.e., filamentous growth) resulted in increased metabolic activity of cells in the confectionary bakery waste stream with agar but decreased metabolic activity in Whey with agar. The best-growing species, Geotrichum candidum, has potential commercial value as a producer of enzymes, biochemicals and lipids and could provide added value while improving the circularity of water and nutrients in food production.

Comparisons of Vibrio fischeri, Photobacterium phosphoreum, and recombinant luminescent using Escherichia coli as BOD measurement

To shorten the time needed to measure biochemical oxygen demand (BOD) in water samples and to provide a rapid feedback of the real condition of water quality, we tested and evaluated the validity and reliability of luminescent bacteria Vibrio fischeri, Photobacterium phosphoreum, and recombinant Escherichia coli as potential indicators of BOD in the domestic wastewaters. The results indicate that the luminescence intensities of these strains are dependent on temperature, pH, and BOD concentration. In comparison to the standard BOD(5) method, the time needed for BOD measurement can be shortened by 90, 120, and 150 min when V. fischeri, P. phosphoreum, and recombinant E. coli, respectively, are used. Recombinant E. coli can be adapted to measure BOD in domestic wastewater containing a wide range of BOD concentrations, V. fischeri is not suitable for measuring diluted wastewater, and P. phosphoreum has only a limited application in measuring concentrated wastewater. To the best of our knowledge, this is the first report in which V. fischeri, P. phosphoreum, and recombinant luminescent E. coli are compared in terms of their potential in BOD measurement systems.