Enhanced lipid production by Rhodosporidium toruloides using different fed-batch feeding strategies with lignocellulosic hydrolysate as the sole carbon source

Abstract

BackgroundIndustrial biotechnology that is able to provide environmentally friendly bio-based products has attracted more attention in replacing petroleum-based industries. Currently, most of the carbon sources used for fermentation-based bioprocesses are obtained from agricultural commodities that are used as foodstuff for human beings. Lignocellulose-derived sugars as the non-food, green, and sustainable alternative carbon sources have great potential to avoid this dilemma for producing the renewable, bio-based hydrocarbon fuel precursors, such as microbial lipid. Efficient bioconversion of lignocellulose-based sugars into lipids is one of the critical parameters for industrial application. Therefore, the fed-batch cultivation, which is a common method used in industrial applications, was investigated to achieve a high cell density culture along with high lipid yield and productivity.ResultsIn this study, several fed-batch strategies were explored to improve lipid production using lignocellulosic hydrolysates derived from corn stover. Compared to the batch culture giving a lipid yield of 0.19 g/g, the dissolved-oxygen-stat feeding mode increased the lipid yield to 0.23 g/g and the lipid productivity to 0.33 g/L/h. The pulse feeding mode further improved lipid productivity to 0.35 g/L/h and the yield to 0.24 g/g. However, the highest lipid yield (0.29 g/g) and productivity (0.4 g/L/h) were achieved using an automated online sugar control feeding mode, which gave a dry cell weight of 54 g/L and lipid content of 59 % (w/w). The major fatty acids of the lipid derived from lignocellulosic hydrolysates were predominately palmitic acid and oleic acid, which are similar to those of conventional oilseed plants.ConclusionsOur results suggest that the fed-batch feeding strategy can strongly influence the lipid production. The online sugar control feeding mode was the most appealing strategy for high cell density, lipid yield, and lipid productivity using lignocellulosic hydrolysates as the sole carbon source.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-016-0542-x) contains supplementary material, which is available to authorized users.

Challenges in lipid production from lignocellulosic biomass using Rhodosporidium sp.; A look at the role of lignocellulosic inhibitors

“…Only a few focus on other types of challenges such as the inhibitor management with respect to some of the substrates that are used for the production of lipids. Due to the limitation of substrate variation, it is necessary to adapt, modify, and develop strains with the aim of improving the utilization of different sugars in hydrolysates obtained from lignocellulosic biomass, as well increasing the tolerance to inhibitory compounds present in them . In this regard, synthetic biology and bioengineering are essential tools to improve the production and adaptation capacities that this strain presents .…”

“…To reduce these feedstock costs, different carbohydrates have been obtained from lignocellulosic biomass from forestry residues . Various studies in the literature have reported the use of different culture media, such as glucose, xylose, crude glycerol, acetic acid, sugarcane juice, and hydrolysates from different kinds of lignocellulosic biomass as well as different cultivation systems (flask, batch, fed, fed‐batch, and pilot) .…”

Life‐cycle analysis of integrated biorefineries with co‐production of biofuels and bio‐based chemicals: co‐product handling methods and implications

“…These IBR designs are chosen as representative examples of biorefineries co‐producing fuels and chemical products. The carbohydrate‐to‐hydrocarbon processes in these IBR designs reflect experimental work focused on oleaginous yeast fermentation at the National Renewable Energy Laboratory, with the ultimate objective to produce fungible drop‐in hydrocarbon biofuels, as one research and development strategy pursued experimentally . The co‐products evaluated here are potential platform chemicals of interest to the bioenergy industry.…”

“…The carbohydrate-to-hydrocarbon processes in these IBR designs reflect experimental work focused on oleaginous yeast fermentation at the National Renewable Energy Laboratory, with the ultimate objective to produce fungible drop-in hydrocarbon biofuels, 3,30,32 as one research and development strategy pursued experimentally. 33 The co-products evaluated here are potential platform chemicals of interest to the bioenergy industry. Succinic acid was initially identified as a top value-added chemical from sugar focused routes in a 2004 Department of Energy-led study.…”

Functional genomics of lipid metabolism in the oleaginous yeastRhodosporidium toruloides

“…R. toruloides is also an attractive host for production of sustainable chemicals and fuels from low-cost lignocellulosic feedstocks. Wild isolates of R. toruloides can produce lipids and carotenoids from a wide variety of carbon sources including glucose (19, 20), xylose (11), and acetate (21), as well as complex biomass hydrolysates (22). They are also relatively tolerant to many forms of stress including osmotic stress (23) and common inhibitors found in hydrolysates produced by common biomass deconstruction technologies, such as dilute acid pretreatment followed by enzymatic saccharification (24, 25).…”