Gaoxiang Qi

Enhanced enzymatic hydrolysis and acetone-butanol-ethanol fermentation of sugarcane bagasse by combined diluted acid with oxidate ammonolysis pretreatment.

This study aims to propose a biorefinery pretreatment technology for the bioconversion of sugarcane bagasse (SB) into biofuels and N-fertilizers. Performance of diluted acid (DA), aqueous ammonia (AA), oxidate ammonolysis (OA) and the combined DA with AA or OA were compared in SB pretreatment by enzymatic hydrolysis, structural characterization and acetone-butanol-ethanol (ABE) fermentation. Results indicated that DA-OA pretreatment improves the digestibility of SB by sufficiently hydrolyzing hemicellulose into fermentable monosaccharides and oxidating lignin into soluble N-fertilizer with high nitrogen content (11.25%) and low C/N ratio (3.39). The enzymatic hydrolysates from DA-OA pretreated SB mainly composed of glucose was more suitable for the production of ABE solvents than the enzymatic hydrolysates from OA pretreated SB containing high ratio of xylose. The fermentation of enzymatic hydrolysates from DA-OA pretreated SB produced 12.12g/L ABE in 120h. These results suggested that SB could be utilized efficient, economic, and environmental by DA-OA pretreatment.

Use of elephant grass (Pennisetum purpureum) acid hydrolysate for microbial oil production by Trichosporon cutaneum

ABSTRACT Elephant grass (Pennisetum purpureum) dilute acid hydrolysate contains 34.6 g/L total sugars. The potential of lipid production by oleaginous yeast Trichosporon cutaneum grown on elephant grass acid hydrolysate was investigated for the first time. During the fermentation process on the elephant grass acid hydrolysate, glucose, xylose, and arabinose could be well utilized as carbon sources by T. cutaneum. Interestingly, xylose was almost no use before glucose was consumed completely. This illustrated that simultaneous saccharification of xylose and glucose by T. cutaneum did not occur on elephant grass acid hydrolysate. The highest biomass, lipid content, lipid yield, and lipid coefficient of T. cutaneum were measured after the sixth day of fermentation and were 22.76 g/L, 24.0%, 5.46 g/L, and 16.1%, respectively. Therefore, elephant grass is a promising raw material for microbial oil production by T. cutaneum.

Preparation of Bacterial Cellulose/Inorganic Gel of Bentonite Composite by In Situ Modification.

To evaluate the possibility of Bacterial cellulose/Inorganic Gel of Bentonite (BC/IGB) composite production using in situ method, the BC/IGB composite was successfully produced by in situ modification of BC in both HS medium and corncob hydrolysate. The results showed that the BC/IGB composite obtained in HS medium (one classical medium for BC production) had a higher water holding capacity, but the water retention capacity of the BC/IGB composite obtained in corncob hydrolysate was better. The performance of BC/IGB composite depended on the environment of in situ modification. Using different media showed significant influence on the sugar utilization and BC yield. In addition, BC/IGB composite produced by in situ method was compared with that produced by ex situ method, and the results shows that water holding capacity of BC/IGB composite obtained through in situ method was better. XRD results showed the crystallinity of BC/IGB composite related little to its performance as water absorbent. Overall, in situ modification is appropriate for further production of BC composite and other clay materials.

Extraction and characterization of wax from sugarcane bagasse and the enzymatic hydrolysis of dewaxed sugarcane bagasse

ABSTRACT Extraction of high-value products from agricultural wastes is an important component for sustainable bioeconomy development. In this study, wax extraction from sugarcane bagasse was performed and the beneficial effect of dewaxing pretreatment on the enzymatic hydrolysis was investigated. About 1.2% (w/w) of crude sugarcane wax was obtained from the sugarcane bagasse using the mixture of petroleum ether and ethanol (mass ratio of 1:1) as the extraction agent. Results of Fourier-transform infrared characterization and gas chromatography–mass spectrometry qualitative analysis showed that the crude sugarcane wax consisted of fatty fractions (fatty acids, fatty aldehydes, hydrocarbons, and esters) and small amount of lignin derivatives. In addition, the effect of dewaxing pretreatment on the enzymatic hydrolysis of sugarcane bagasse was also investigated. The digestibilities of cellulose and xylan in dewaxed sugarcane bagasse were 18.7 and 10.3%, respectively, compared with those of 13.1 and 8.9% obtained from native sugarcane bagasse. The dewaxed sugarcane bagasse became more accessible to enzyme due to the disruption of the outermost layer of the waxy materials.

Liquefaction and characterization of residue of oleaginous yeast in polyhydric alcohols

The residue of oleaginous yeast (ROY) was liquefied in polyhydric alcohols using sulfuric acid as catalyst. The effects of some liquefaction conditions on the liquefied residue rate, such as liquefaction temperature, catalyst loading, reaction time, glycerol concentration and solvent/ROY ratio, were discussed. The liquefied residue rate decreased as the reaction time, liquefaction temperature, catalyst loading, solvent/ROY ratio increased. The re-polymerization of liquefied products was favored in later stage reaction. Higher catalyst loading and lower solvent/ROY ratio could accelerate the re-polymerization of liquefied products; thus the liquefied residue increased. Fourier transform infrared (FT-IR) analyses showed that the main component of ROY is polysaccharide. The gas chromatography and mass spectrometry (GC-MS) analysis showed that liquefied products of ROY included alcohols, acids, ketones, aldehydes, amide, ester and their derivatives.

The hydrolytic efficiency and synergistic action of recombinant xylan-degrading enzymes on xylan isolated from sugarcane bagasse

Understanding the interaction mechanisms between xylan and xylan-degrading enzymes is beneficial to the efficient hydrolysis of xylan. Xylan from sugarcane bagasse (SB) was extracted and characterized. The effects of heat treatment and removal of side chains of SB xylan on the hydrolytic efficiency and synergistic action of endo-β-1,4-xylanases (HoXyn11A and AnXyn10C), β-xylosidases (AnXln3D), and α-l-arabinofuranosidases (AnAxh62A) were investigated. Results indicated that heat treatment of xylan can improve the hydrolytic efficiency of xylan-degrading enzymes, and it is essential for the efficient hydrolysis of xylan by HoXyn11A. The removal of arabinofuranosyl side chains of xylan by AnAxh62A before enzymatic hydrolysis reduced the hydrolytic efficiency of HoXyn11A and AnXyn10C on xylan. AnXyn10C was more efficient than HoXyn11A in hydrolysis of xylan, whereas HoXyn11A showed better synergistic action than AnXyn10C with AnAxh62A and AnXln3D in the hydrolysis of xylan. This study provides new insights on the enzymatic hydrolysis of SB into monosaccharides and xylo-oligosaccharides.

Lumping kinetics of ABE fermentation wastewater treatment by oleaginous yeast Trichosporon cutaneum

ABSTRACT Lumping kinetics models were built for the biological treatment of acetone–butanol–ethanol (ABE) fermentation wastewater by oleaginous yeast Trichosporon cutaneum with different fermentation temperatures. Compared with high temperature (33°C, 306 K) and low temperature (23°C, 296 K), medium temperature (28°C, 301 K) was beneficial for the cell growth and chemical oxygen demand (COD) degradation during the early stage of fermentation but the final yeast biomass and COD removal were influenced little. By lumping method, the materials in the bioconversion network were divided into five lumps (COD, lipid, polysaccharide, other intracellular products, other extracellular products), and the nine rate constants (k1–k9) for the models can well explain the bioconversion laws. The Gibbs free energy (G) for this bioconversion was positive, showing that it cannot happen spontaneous, but the existence of yeast can after the chemical equilibrium and make the bioconversion to be possible. Overall, the possibility of using lumping kinetics for elucidating the laws of materials conversion in the biological treatment of ABE fermentation wastewater by T. cutaneum has been initially proved and this method has great potential for further application.

Efficient bioconversion from acid hydrolysate of waste oleaginous yeast biomass after microbial oil extraction to bacterial cellulose by Komagataeibacter xylinus

ABSTRACT Biomass acid hydrolysate of oleaginous yeast Trichosporon cutaneum after microbial oil extraction was applied as substrate for bacterial cellulose (BC) production by Komagataeibacter xylinus (also named as Gluconacetobacter xylinus previously) for the first time. BC was synthesized in static culture for 10 days, and the maximum BC yield (2.9 g/L) was got at the 4th day of fermentation. Most carbon sources in the substrate (glucose, mannose, formic acid, acetic acid) can be utilized by K. xylinus. The highest chemical oxygen demand (COD) removal (40.7 ± 3.0%) was obtained at the 6th day of fermentation, and then the COD increased possibly due to the degradation of BC. The highest BC yield on COD consumption was 38.7 ± 4.0% (w/w), suggesting that this is one efficient bioconversion for BC production. The BC structure was affected little by the substrate by comparison with that generated in classical HS medium using field-emission scanning electron microscope (FE-SEM), Fourier transform infrared, and X-ray diffraction. Overall, this technology can both solve the issue of waste oleaginous yeast biomass and produce valuable biopolymer (BC).

Elucidating the Beneficial Effect of Corncob Acid Hydrolysate Environment on Lipid Fermentation of Trichosporon dermatis by Method of Cell Biology

In present study, the beneficial effect of corncob acid hydrolysate environment on lipid fermentation of Trichosporon dermatis was elucidated by method of cell biology (mainly using flow cytometry and microscope) for the first time. Propidium iodide (PI) and rhodamine 123 (Rh123) staining showed that corncob acid hydrolysate environment was favorable for the cell membrane integrity and mitochondrial membrane potential of T. dermatis and thus made its lipid fermentation more efficient. Nile red (NR) staining showed that corncob acid hydrolysate environment made the lipid accumulation of T. dermatis slower, but this influence was not serious. Moreover, the cell morphology of T. dermatis elongated in the corncob acid hydrolysate, but the cell morphology changed as elliptical-like during fermentation. Overall, this work offers one simple and effective method to evaluate the influence of lignocellulosic hydrolysates environment on lipid fermentation.