Tobacco Leaf Protein: II. Genetic and Fractionation Approaches to Improving Tobacco Leaf Protein Production

Tobacco variety T. I. 401 was evaluated for seasonal leaf protein yields and crossbred with other genotypes to determine whether leaf protein yield was a genetically transmissible trait. Relatively high leaf protein yields associated with later maturity were observed in preliminary trials but additional crossbreeding and selection is deemed necessary to achieve stable integration of improved leaf protein yields and desirable agronomic performance. Chromatographic and electrophoretic analyses demonstrated that high leaf protein yield of T. I. 401 was not associated with a particular protein fraction but rather was a general phenomenon affecting all major protein classes. Besides examining genetic factors for improving leaf protein yields, two mechanical improvements in leaf protein fractionation technology were introduced into the process. A mild acidification step (to pH 5.5) with a subsequent moderate heat treatment (50°C) resulted in a green coagulum which was readily removed by brief low speed centrifugation without substantial loss of the fraction containing soluble protein which precipitates as a white pellet when heated to 80°C. Hollow-fiber membrane technology was also investigated as a means of producing a purified concentrate with high levels of undegraded protein. The membrane system tested was relatively efficient and greatly improved the quality of the Protein product.