A self-designed horizontal rotating bioreactor (HRR) was applied for enzymatic hydrolysis of pretreated corn stover to improve the process economics of ethanol production. The mixing principle was based on gravity and free fall employed with tank-rotating. The liquefaction performances using the HRR and the vertical stirred-tank reactor (VSTR) with a helical impeller were compared and analyzed by measuring rheological properties of the slurry. During the enzymatic hydrolysis, viscosity decreased dramatically in the initial phase for both bioreactors and more pronouncedly for the HRR. Rheological parameters fitted to the power law showed that shear thinning properties of the slurry weakened during the reaction. The glucose concentration was used to define the efficiency of the saccharification reaction. The HRR also proved to be more efficient for glucose release with both the constant and fed-batch substrate addition modes. Liquefaction and saccharification at 25 % w/w dry matter (DM) and enzyme loading of 7 FPU/g DM resulted in the optimal glucose concentration of 86 g/kg. Results revealed a decrease in cellulose conversion at increasing initial DM, which was slighter in the HRR compared with that in the VSTR.

The enzymatic hydrolysis of lignocelluloses is a key step in the production of ethanol. Economic considerations for large-scale implementation of the process require operation at high solid concentrations. However, the decrease in cellulose conversion offsets the advantages of working at high solid concentrations. The conversion showed a linear decrease in the reaction of pretreated corn stover (PCS) from 2 to 20 % (w/w) and filter paper from 1 to 10 % (w/w) initial total solid content. Hydrolysis experiments with PCS at various mixing speeds showed that the mass transfer limitation could not restrict the cellulose conversion except the solid concentrations over 5 % DM(w/w). The lignin, if added separately, does not correspond directly to the decrease. At increased concentrations, furfural and 5-hydroxymethylfurfural played a part in the effect, and 5-hydroxymethylfurfural only affected exoglucanase. Product inhibition caused by glucose accumulation at increased solid concentrations was found to be a significant and perhaps principal factor. The decrease in yield was caused by the synergetic inhibition, which was more serious with increased solid concentrations.

Column chromatography and reversed-phase HPLC using a Sepax BR-C18 column were applied for the analysis of glycerides in the docosahexaenoic acid (DHA) oil by Schizochytrium sp. The oil was detected under UV light after isocratic elution with 20 % 2-propanol/hexane (5:4, v/v) + 80 % acetonitrile. The correlation coefficients for the calibration of HPLC for DHA glycerides were in the range of 0.9958–0.9998. The accuracy was confirmed with recoveries of 93.47–102.25 %. DHA oil samples under different aeration rates were successfully analyzed and the content of the binding of DHA on the acylglycerol backbone was very low (1.81–4.21 %). However, the content of glycerides (tri-, di-, mono-) separated by column chromatography was more than 87.22 %. The glycerides were largely composed of triacylglycerides (TAG) (82.29–89.54 %), where higher content of TAG correlated to higher contents of DHA and TAG of DHA (TriDHA). In addition, the optimal aeration rate of 250 m3/h was obtained for TAG, DHA, and TriDHA production by Schizochytrium sp. with the temperature 30 ± 0.5 °C, impeller speed 85 ± 5 rpm and pressure 0.04 Mpa.

Microalgal oil was encapsulated in gelatin-gum Arabic complex coacervated matrices using transglutaminase (TG) as cross-linking agent. The effects of various cross-linking parameters including hardening time, temperature, pH and TG concentration on the oil release rate of the complex coacervation microcapsules (CCMs) were investigated, with sodium dodecyl sulfate (SDS) as release medium. The optimum parameters were as follows: hardening for 6 h at 15 °C and pH 6.0 with TG concentration of 15 U/g gelatin. The microcapsules obtained under optimum conditions had the lowest oil release rate. By analyzing the oil release curves, it was found that the oil release rate did not exactly fit the modified first-order kinetic model but exhibited early time and late time approximations for unsteady state diffusion. A greater initial release of oil was clearly observed whatever cross-linking parameters were, while the release profile became constant indicating some sustained release after the first hour.Graphical abstractHighlights► Complex coacervation system can better encapsulate and protect the microalgal oil. ► The cross-linking parameters affect the oil release rate of the complex coacervation microcapsules (CCMs). ► Kinetics of oil release from CCMs.

Lignins were isolated and purified from alkali treated prehydrolysate of corn stover. The paper presents the structural features of lignins in a series purification processes. Fourier transform infrared spectroscopy, ultraviolet-vis spectroscopy and proton nuclear magnetic resonance spectroscopy were used to analyze the chemical structure. Ther-mogravimetric analysis was applied to follow the thermal degradation, and wet chemical method was used to determine the sugar content. The results showed that the crude lignin from the prehydrolysate of corn stover was a heterogeneous material of syringyl, guaiacyl and p-hydroxyphenyl units, containing associated polysaccharides, lipids, and melted salts. Some of the crude lignin was chemically linked to hemicelluloses (mainly xylan). The lipids in crude lignin were probably composed of saturated and/or unsaturated long carbon chains, fatty acids, triterpenols, waxes, and derivatives of aromatic. The sugar content of purified lignin was less than 2.11%, mainly composed of guaiacyl units. DTGmax of puri-fied lignin was 359 °C. The majority of the hydroxyl groups were phenolic hydroxyl groups. The main type of linkages in purified lignin was β-O-4. Other types of linkages included β-5, β-β and a-O-4.