The disclosure discloses a method for increasing the intracellular heme content of Escherichia coli and belongs to the field of metabolic engineering. In the disclosure, in E. coli, the gene mscS encoding a small conductance mechanically sensitive ion channel protein is knocked out, the gene aroG encoding 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase is knocked out, or the gene hemA encoding glutamyl-tRNA reductase is overexpressed. The constructed recombinant strain is cultured in an LB culture medium, and the heme content can reach 47.6 mol.Math.L.sup.1, which is significantly higher than that of a control strain. The recombinant strain has the value of wide application.

The transgenic plants engineered to express animal-derived proteins, such as myoglobin, casein, chymosin, hemoglobin and actin and other animal-derived proteins, and the nucleic acids encoding the same are described herein. Methods of making and identifying the transgenic plants, processing the seeds from the transgenic plants that contain the expressed animal-derived proteins, isolating and purifying the expressed proteins, and utilizing the expressed proteins in food are provided. Food and food ingredients that include myoglobin, casein, chymosin, hemoglobin and actin are also disclosed herein. Genes encoding myoglobin, casein, hemoglobin and actin forms that have been modified to improve performance as components of food are described.

Plants and plant tissue such as leaves comprising leghemoglobin are produced by modifying the genome of the plant or introducing leghemoglobin coding or regulatory sequences into the plant. Plants, leaves, fruits, tubers, roots, seeds, and protein compositions comprising leghemoglobin are provided. Protein compositions comprising leghemoglobin, such as isolates and concentrates, can be made from the plants, tissue, fruits, tubers, roots, seeds and leaves. Additionally, methods for generating and using plants, tissue, fruits, tubers, roots, seeds, leaves and protein compositions comprising leghemoglobin are disclosed.

The present disclosure relates to genetically modified bacteria, wherein said genetically modified bacteria is designed to express or overexpress a heme-containing protein. Said protein is optionally expressed or overexpressed in combination with one or more enzymes that catalyze the heme synthesis pathway. Said genetically modified organism allows scalable production of heme-containing protein with the advantage that the expressed protein remains in soluble form without forming inclusion bodies.