Carbohydrate analysis of Mortierella alpina by colorimetry and HPLC-ELSD to reveal accumulation differences of sugar and lipid.

To establish reliable methods for the extraction and quantification of the total carbohydrate and intracellular saccharides from Mortierella alpina and study the changes between carbohydrate and lipid in fermentation process. The extraction of mycelia with HCl following a photometric phenol–sulphuric acid reaction was identified as an optimal method for total carbohydrate analysis in Mortierella alpina, which the extraction efficiency performed 1.1–3.6 fold than other five methods. The total carbohydrate content increased from initial 19.26 to 25.86% during early fermentation process and declined gradually thereafter, while the fatty acid was increasing from 8.47 to 31.03%. For separation and qualitative estimation of intracellular saccharides, the acetonitrile/water freeze–thaw method for extraction and Sugar-Pak I column for separation proved to be possible. With the glucose rapidly decreasing at the beginning of growth, the trehalose accumulated rapidly from 1.63 to 5.04% and then decreased slightly but maintain above 4% of dry biomass. This work established comprehensive carbohydrate extraction and analysis methods of Mortierella alpina and identified the main saccharide in fermentation process which indicated that the accumulation of fatty acids was related to the change of intracellular carbohydrate content.