Maximizing the simultaneous production of lipids and carotenoids by Rhodosporidium toruloides from wheat straw hydrolysate and perspectives for large-scale implementation

Xylitol can be obtained from hemicelullosic fraction of lignocellulosic materials containing D-xylose. Formic acid hydrolysis is widely used in lignocellulose pretreatment. However, formic acid hydrolysis wheat straw cannot be directly used as fermentation subsequently owing to various fermentation inhibitors, especially the formic acid in reaction system and released during pretreatment. This study describes main hydrolysis components and inhibitors prepared by hydrolysis of wheat straw with formic acid solution, and different detoxification methods ware used to romve the inhibitors. Study found treatment of wheat straw hydrolysate with overliming treatment and D311 ion-exchange resin had a good result on reduction formic acid and other main inhibitors, results showed which can eliminate 94% of residual formic acid and with only 15% reducion of xylose. To verify the effectiveness of different detoxification methods, hydrolysates of detoxification werr fermented by Candida.tropicalis AS2.1776, and the results also found that the hydrolysate treatmented with overliming treatment and D311 ion-exchange resin have the hightest xylitol yield.

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Metabolic engineering of Aspergillus niger via ribonucleoprotein-based CRISPR–Cas9 system for succinic acid production from renewable biomass

Biotechnology for Biofuels ◽

10.1186/s13068-020-01850-5 ◽

2020 ◽

Vol 13 (1) ◽

Author(s):

Lei Yang ◽

Mikkel Møller Henriksen ◽

Rasmus Syrach Hansen ◽

Mette Lübeck ◽

Jesper Vang ◽

...

Keyword(s):

Aspergillus Niger ◽

Succinic Acid ◽

Wheat Straw ◽

Acid Production ◽

Value Added ◽

Fungal Cell ◽

Renewable Biomass ◽

Succinic Acid Production ◽

Wheat Straw Hydrolysate ◽

Low Culture

Abstract Background Succinic acid has great potential to be a new bio-based building block for deriving a number of value-added chemicals in industry. Bio-based succinic acid production from renewable biomass can provide a feasible approach to partially alleviate the dependence of global manufacturing on petroleum refinery. To improve the economics of biological processes, we attempted to explore possible solutions with a fungal cell platform. In this study, Aspergillus niger, a well-known industrial production organism for bio-based organic acids, was exploited for its potential for succinic acid production. Results With a ribonucleoprotein (RNP)-based CRISPR–Cas9 system, consecutive genetic manipulations were realized in engineering of the citric acid-producing strain A. niger ATCC 1015. Two genes involved in production of two byproducts, gluconic acid and oxalic acid, were disrupted. In addition, an efficient C4-dicarboxylate transporter and a soluble NADH-dependent fumarate reductase were overexpressed. The resulting strain SAP-3 produced 17 g/L succinic acid while there was no succinic acid detected at a measurable level in the wild-type strain using a synthetic substrate. Furthermore, two cultivation parameters, temperature and pH, were investigated for their effects on succinic acid production. The highest amount of succinic acid was obtained at 35 °C after 3 days, and low culture pH had inhibitory effects on succinic acid production. Two types of renewable biomass were explored as substrates for succinic acid production. After 6 days, the SAP-3 strain was capable of producing 23 g/L and 9 g/L succinic acid from sugar beet molasses and wheat straw hydrolysate, respectively. Conclusions In this study, we have successfully applied the RNP-based CRISPR–Cas9 system in genetic engineering of A. niger and significantly improved the succinic acid production in the engineered strain. The studies on cultivation parameters revealed the impacts of pH and temperature on succinic acid production and the future challenges in strain development. The feasibility of using renewable biomass for succinic acid production by A. niger has been demonstrated with molasses and wheat straw hydrolysate.

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