Influence of the development stage of the plant biomass for protein yield in a green biorefinery.

Summary

The scarce availability of organic animal feed for monogastric animals is hindering the development of organic farming in many regions. A green biorefinery platform called OrganoFinery aims at producing organic protein-rich animal feed based on organically grown green biomass. The freshly harvested green biomass is separated into a solid fraction (press cake) and a liquid fraction (green juice). Subsequently, the green juice is inoculated with specific lactic acid bacteria which ferment the soluble sugars into lactic acid triggering a pH drop and thus, the precipitation of proteins. Last, proteins are extracted by centrifugation and the organic protein concentrate is suitable for feeding monogastric animals.
Green perennial crops can be harvested several times during a season. In the present study, the impact of the development stage of the plant biomass, exemplified by red clover, at harvesting time for the protein extraction yield was assessed in order to develop a harvesting strategy. Red clover was harvested at different developmental stages i.e. early stem elongation, late stem elongation and heading. Right after harvest, the fresh biomass was processed to produce a protein concentrate as described above.
The green juices presented higher concentration of soluble proteins and soluble sugars with increasing maturity. After 10 hours fermentation, the pH dropped from 5.9-6.0 to 3.9-4.0 in all green juice samples and the lactic acid concentration reached up to 20.6 g/L. The highest lactic acid concentration (20.6 g/L) was achieved for the late maturity stage and was 1.5 higher than in the early maturity stage. Differences due to the development stage were also observed in the recovery of proteins from the green juice into the protein concentrate. Indeed, the recovery of proteins from the green juice was between 70-80% of the content in the green juice and with the highest values obtained for the late maturity stage.
The relevance of this study relies on the fact that the harvesting strategy is crucial in order to maximize the protein yield from green biomass and, to develop an economically viable green biorefinery platform to produce organic protein-rich feed for monogastric animals.