Medium optimization for biomass production of three peat moss (Sphagnum L.) species using fractional factorial design and response surface methodology

Peat moss (Sphagnum) biomass is a promising bioresource of renewable material to substitute peat in growing media. For sustainable production on a large scale, the productivity of Sphagnum mosses has to be increased by optimizing culture conditions. Optimization was achieved using experimental design to determine concentrations of eight factors leading to highest biomass yield. We improved an established Sphagnum medium by reducing the concentrations of NH$_{4}$NO$_{3}$, KH$_{2}$PO$_{4}$, KCl, MgSO$_{4}$, Ca(NO$_{3}$)$_{2}$, FeSO$_{4}$ and a microelement solution up to 50%. Together with sucrose concentrations of 16 g L$^{-1}$ for Sphagnum fuscum and 20 g L$^{-1}$ for Sphagnum palustre and Sphagnum squarrosum, moss productivities were enhanced for all tested species in shake flasks. Further upscaling to 5 L photobioreactors increased the biomass yield: 15 g freshweight resulted in about 630 g for S. fuscum (50-fold), 580 g for S. palustre (40-fold) and 400 g for S. squarrosum (25-fold) in 24 days.