Hemicellulose sugar recovery from steam-exploded wheat straw for microbial oil production

There are currently few successful examples of using straw hemicellulose as a carbon source in the fermentation industry. In this paper, hemicellulose hydrolysates were recovered from steam-exploded wheat straw (SEWS) and used to produce microbial oil. The effects of the steam explosion treatment conditions, the elution temperature and the ratio of elution water to SEWS on sugar recovery were examined. A broth with 3.8 g l−1 of reducing sugar and 22.3 g l−1 of total soluble sugars was obtained with a 10-fold excess (w/w) of water at 40 °C to wash the SEWS treated under steam explosion conditions at 200 °C for 5 min. This broth was used to produce microbial oil by the oleaginous fungus Microsphaeropsis sp., which was able to secrete xylanase to degrade oligosaccharides from straw hemicellulose and accumulate microbial oil. Under optimized conditions, the oil concentration was 2.6 g l−1. The yield of oil from sugar consumed was 0.14 g g−1. The microbial oil produced by this research could be used as feedstock for biodiesel production because the microbial oil was primarily composed of neutral lipids. This research establishes a novel protocol for microbial oil production from straw hemicellulose.

► We explored a novel way for microbial oil production from hemicellulose sugars recovered from steam-exploded wheat straw (SEWS).
► These hemicellulose sugars were good carbon source for the production of microbial oil by the oleaginous fungus Microsphaeropsis sp. which was able to secret xylanase to degrade oligosaccharides and accumulate microbial oil.
► This research explored not only a new way of utilization of the hemicellulose of straw but also a new approach for the production of microbial oil that is a potential feedstock for biodiesel production.