It is necessary to develop and deploy novel protein production to allow the establishment of a sustainable supply for both humans and animals, given the ongoing expansion of protein demand to meet the future needs of the increased world population and high living standards. In addition to plant seeds, green biomass from dedicated crops or green agricultural waste is also available as an alternative source to fulfill the protein and nutrient needs of humans and animals. The development of extraction and precipitation methods (such as microwave coagulation) for chloroplast and cytoplasmic proteins, which constitute the bulk of leaf protein, will allow the production of leaf protein concentrates (LPC) and protein isolates (LPI). Obtained LPC serves as a sustainable alternative source of animal-based protein besides being an important source of many vital phytochemicals, including vitamins and substances with nutritional and pharmacological effects. Along with it, the production of LPC, directly or indirectly, supports sustainability and circular economy concepts. However, the quantity and quality of LPC largely depend on several factors, including plant species, extraction and precipitation techniques, harvest time, and growing season. This paper provides an overview of the history of green biomass-derived protein from the early green fodder mill concept by Károly Ereky to the state-of-art of green-based protein utilization. It highlights potential approaches for enhancing LPC production, including dedicated plant species, associated extraction methods, selection of optimal technologies, and best combination approaches for improving leaf protein isolation.

Green leaves from legumes and grasses have long been recognized as potential sources of protein for feed and food. Selecting an appropriate processing method is crucial for protein concentration and can also affect the composition of phytonutrients important for human and animal health. This study examines the extraction of leaf protein concentrate (LPC) from a mixture of fresh vetch-triticale biomass, using microwave coagulation (MWC) as the control method compared to fermentation processes, including lactic acid fermentation (LAF), induced Lactobacillus fermentation (LBF), and yeast-bacteria fermentation (YLBF). MWC yielded a higher percentage (11.2 %) of macroaggregate-containing LPCs with a crude protein content of 44.78 m/m%. The crude protein content of post-fermentation LPCs ranged from 35.14 to 38.50 m/m%, but SDS-PAGE analysis revealed that these LPCs were more readily solubilizable and contained higher levels of essential amino acids, such as methionine and isoleucine. Fermentation processes were also more effective at converting flavonoids into health-promoting aglycones, including chrysoeriol (248.5–283.9 μg g⁻¹), luteolin (242.6–304.1 μg g⁻¹), and isovitexin (72.6–91.6 μg g⁻¹). Among the fermentation methods, LBF and YLBF were preferable for accumulating these health-promoting flavonoids.