DNA storage of digital media using composite DNA. composite DNA storage

DNA, with its remarkable density and long-term stability, is an appealing potential next generation data storage medium, most notably for long-term archiving. Megabyte scale DNA based storage was first reported in 2012. A recent study recently demonstrated a DNA based storage system that achieves, using fountain codes, a Shannon capacity of ~1.57 bits per base. However, synthesis and sequencing technologies process multiple nominally identical molecules in parallel, leading to significant information redundancies. We introduce composite DNA alphabets, using mixed DNA base types, to leverage this redundancy, enabling the encoding of data in fewer synthesis cycles. We develop encoding and decoding for composite DNA based storage, including error correction. Using current DNA synthesis technologies, we code 6.4 Megabyte data into composite DNA, achieving a ~25% improvement in the total synthesis needed per unit of data, as compared to literature. We further demonstrate, on smaller scales, how flexible synthesis leads to a 2.7 fold decrease in the number of synthesis cycles required for storing a unit of data. Using simulated encoding with experimentally derived error rates, we examine the potential benefits of larger composite alphabets. Composite DNA can thus reduce costs for DNA based storage and can also serve in other applications of synthetic DNA.