Use of Orthogonal Array Composite Designs to Study Lipid Accumulation in a Cell‐Free System

The development of clean, sustainable alternative energy sources is increasingly important. One promising alternative to depleting fuel reserves is algae‐based biodiesel fuel, which is both non‐toxic and renewable. Despite the tremendous potential of algae‐based biodiesel fuel, it has not yet been profitable because of the high cost per unit area of large cultivation. We present a novel application of Orthogonal Array Composite Designs (OACDs) to optimize lipid production of a cell‐free system for algae. An OACD consists of a two‐level fractional factorial design and a three‐level orthogonal array. We start with an initial screening experiment based on six chemicals using an OACD with 50 runs. Based on this experiment, two chemical compounds were removed and a follow‐up 25‐run OACD with four chemicals was performed. Our analysis shows that only three chemicals – nitrogen, magnesium, and phosphate – are essential for lipid accumulation, and a range of optimum combinations of these three chemicals is identified. The lipid accumulation for these three chemical combinations is substantially higher in comparison to the commercial medium, which contains 16 chemicals and soil water. This leads to a reduced cost of the chemical medium and increased efficiency of biodiesel production from the algal‐based cell‐free system, which can be used to significantly expand the use of biodiesel as a viable alternative to fossil fuels. Copyright © 2015 John Wiley & Sons, Ltd.