Evaluation of RuBisCO extraction methods using the aquatic plant, Lemna

Lemna minor, most commonly known as duckweed belongs to the family Lemnaceae is generally used as source of food for several aquatic inhabitants and in waste water treatment. Duckweed is also potentially a high quality protein source for human nutrition. Company X has developed a unique approach to capture the nutritive component of Lemna and transforming it into highly sustainable food products for future generations. Ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO) protein was extracted from Lemna using two different procedures: 1) ammonium sulfate precipitation, and 2) heat coagulation of insoluble suspended solids (a protocol developed by NIZO food research center). Objective: To identify an efficient method to extract RuBisCO protein from Lemna for incorporation into food formulations. Methods: Ammonium sulfate precipitation and heat coagulation procedures were tested to purify RuBisCO from Lemna. SDS PAGE analysis was implemented to trace loss of RuBisCO through different stages of the extraction process. Crude protein content and functional properties like foaming and emulsion stability were evaluated to determine its sustainability as potential protein alternative for food industries. Results: While SDS PAGE profiles displayed that there was no significant loss of protein observed in either of the extraction methods, analysis using ImageJ software showed a higher relative purity of 59.52% RuBisCO by Nizo method. Extraction yield on wet-basis for ammonium sulfate precipitation and heat coagulation methods was estimated to be 1.02 g and 6.48 g per 500g of plant biomass. In addition, crude protein content of ammonium sulfate precipitation and Nizo method was 100.99 % and 34.41 % respectively. Furthermore, Nizo protein isolates exhibited excellent foaming capacity, foaming stability and emulsion stability of 93.3%, 60.1% and 50.6 % respectively. Conclusion: SDS PAGE analysis indicated that there was no protein loss in the waste streams of either extraction method, relatively higher purity of 59.52% protein was extracted with Nizo method. In addition, a high yield (by mass) of protein with minimal sample handling and extraction time was obtained using the Nizo method indicating it is a more promising and efficient protocol for extraction of RuBisCO from Lemna.