Abstract
Currently, hydrogen-oxidizing bacteria (HOB) based power-to-protein is a promising approach to produce alternative microbial protein (MP), however, the nitrogen source used was either derived from commercial products or was firstly recovered from waste streams and then diluted for HOB growth. In the present study, simultaneous ammonium recovery from wastewater and in-situ utilization for the green MP (derived from Cupriavidus necator 335) production was successfully demonstrated using a microbial electrochemical recovery conversion cell (MERC). 0.41 ∼ 0.82 g/L of dried biomass (protein content 49 ∼ 63%) was yielded in 36 h with a power supply of 3, 4, and 5 V. C. necator 335 could grow in the MERC system receiving wastewater with a broad range of ammonium (0.05 ∼ 8 g N/L) and the highest biomass production of 0.9 g/L (protein content 54%) was achieved at 2 g N/L. 2.69 g/L of dried biomass containing 57% protein was obtained in 120 h with an initial supply of 1 L CO2 and 2 g N-NH4+. Applied voltages and ammonium concentrations showed a minor impact on the amino acid profile. Furthermore, the MERC system was tested with real waste streams (e. g., municipal wastewater, and digestate) and 0.45 ∼ 1.22 g biomass/L (protein content 52 ∼ 62%) were harvested. The characteristics of the wastewater streams (e. g., ammonium concentration and conductivity) could significantly affect the system performances. The harvested MP from real wastewater showed a high quality of amino acid profile and implied a potential in substituting traditional plant/animal-based protein.
Highlights
It is predicted that the world’s population will keep growing and by 2050 there will be 9 billion people on the planet [1]
Alloy mesh (4 × 4 cm) coated with IrO2 was used as the anodic electrode, and titanium mesh (4 × 4 cm) was used as the cathodic electrode (Fig. 1). 170 mL of ammonium sulfate-rich synthetic wastewater was used as anolyte while the same volume of nitrogen-free medium was used as catholyte for hydrogen-oxidizing bacteria (HOB) cultivation
With a power supply of higher than 3 V, protein-rich biomass was produced in the form of the hydrogen oxidizing bacterial (HOB) strain C. necator 335, in the cathode chamber
Summary
It is predicted that the world’s population will keep growing and by 2050 there will be 9 billion people on the planet [1]. As a consequence of the increasing world population, the demand for high-quality protein will be doubled by 2050 [2]. Conventional protein production activities are intensifying various environmental issues. A vast amount of fertilizers, pesticides, herbicides, and anti biotics have to be introduced to the processes to ensure high produc tivity and yield, resulting in negative impacts on water and soil environments and human health [3]. The agriculture sector contributed to about 13.5% of greenhouse gases (GHG) emissions [4], increasing the global concern about climate change. The conventional ways of protein production are prone to be interfered by extreme weather (e.g., drought, waterlog, and flood). A more sustainable way of protein production is urgently needed
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