Integrated alkali pretreatment and preservation of wet lettuce (Pistia stratiotes) by lactic acid bacteria for fermentable sugar production

An integrated process was proposed by applying NaOH at high solid condition followed by ensilage to pretreat and preserve the biomass of water lettuce for fermentable sugar production. The results showed that the pretreatment with sodium hydroxide prior the inoculation of lactic acid bacteria effectively removed the lignin content from biomass of water lettuce and increased the extractable portion of the biomass. Experimental sets that had received alkali pretreatment had more total organic acids and fewer butyric acids generated than non-pretreated sets. The results also showed that the integrated process can preserve more carbohydrate content of biomass and can give higher fermentable sugar yields than without pretreatment. Overall, the study suggests that treatment with NaOH improves preservation of fresh harvested water lettuce but further investigation of optimal conditions is needed.     

Optimization of dilute acid and enzymatic hydrolysis for dark fermentative hydrogen production from the empty fruit bunch of oil palm

Pretreatment of the empty fruit brunch (EFB) from oil palm was investigated for H₂ fermentation. The EFB was hydrolyzed at various temperatures, H₂SO₄ concentrations, and reaction times. Subsequently, the acid-hydrolysate underwent enzymatic saccharification under various temperature, pH, and enzymatic loading conditions. Response surface methodology derived the optimum sugar concentration (SC), hydrogen production rate (HPR), and hydrogen yield (HY) as 28.30 g L⁻¹, 2601.24 mL H₂ L⁻¹d⁻¹, and 275.75 mL H₂ g⁻¹ total sugar (TS), respectively, at 120 °C, 60 min of reaction, and 6 vol% H₂SO₄, with the combined severity factor of 1.75. Enzymatic hydrolysis enhanced the SC, HY, and HPR to 34.52 g L⁻¹, 283.91 mL H₂ g⁻¹ TS, and 3266.86 mL H₂ L⁻¹d⁻¹, respectively, at 45 °C, pH 5.0, and 1.17 mg enzyme mL⁻¹. Dilute acid hydrolysis would be a viable pretreatment for biohydrogen production from EFB. Subsequent enzymatic hydrolysis can be performed if enhanced HPR is required.     

Establishment and verification of a shrinking core model for dilute acid hydrolysis of lignocellulose

The kinetics of lignocellulose hydrolysis under the conditions of high temperature and dilute acid (mass fraction 0.05%) was investigated in this paper. By studying the reducing sugar concentration versus reaction temperature (170°C–220°C) and reaction time (150–1800 s) during the hydrolysis process of five kinds of crop straw (rice, wheat, cotton, rape and corn), the shrinking core model was established, and the differential equation of the model and its analytical solution were obtained. With a numerical calculation method, the kinetic equation was estimated, and the degradation of reducing sugar obeyed first-order kinetics was obtained. The calculated results from the equations agreed well with the original experimental data. The calculation by the model showed that the reducing sugar concentration increases as the size of the particles decrease, and the uniform particles increase.     

Kinetic characterization for hemicellulose hydrolysis of corn stover in a dilute acid cycle spray flow-through reactor at moderate conditions

The kinetic characterization of hemicellulose hydrolysis of corn stover was investigated using a new reactor of dilute acid cycle spray flow-through (DCF) pretreatment. The primary purpose was to obtain kinetic data for hemicellulose hydrolysis with sulfuric acid concentrations (10-30 kg m⁻³) at relatively low temperatures (90-100 °C). A simplified kinetic model was used to describe its performance at moderate conditions. The results indicate that the rates of xylose formation and degradation are sensitive to flow rate, temperature and acid concentration. Moreover, the kinetic data of hemicellulose hydrolysis fit a first-order reaction model and the experimental data with actual acid concentration after accounting for the neutralization effect of the substrates at different temperatures. Over 90% of the xylose monomer yield and below 5.5% of degradation product (furfural) yield were observed in this reactor. Kinetic constants for hemicellulose hydrolysis models were analyzed by an Arrhenius-type equation, and the activation energy of xylose formation were 111.6 kJ mol⁻¹, and 95.7 kJ mol⁻¹ for xylose degradation, respectively.     

大米草浓酸水解及发酵生产生物燃料的初步研究

探讨了大米草浓酸水解的影响因素,采用正交试验优化得到了大米草最佳水解条件:硫酸质量分数为50%、水解时间为60min、水浴温度为50℃、大米草粒径为10～20目、固液质量比为1:9,此时糖的得率达36%.利用基因工程菌6508-127发酵大米草水解液生产燃料酒精,产率为8.9 g/100 g(乙醇/大米草);利用圆红冬孢酵母As2.1389发酵大米草水解液生产生物油脂,产率为6.4 g/100 g(油脂/大米草).     

Apricot Kernel shell waste treated with phosphoric acid used as a green,metal-free catalyst for hydrogen generation from hydrolysis of sodium borohydride

In this study, grinded apricot kernel shell (GAKS) biobased waste was used for the first time as a cost-effective, efficient, green and metal-free catalyst for hydrogen generation from the hydrolysis reaction of sodium borohydride (NaBH₄). For the hydrogen production by NaBH₄ hydrolysis reaction, GAKS was treated with various acids (HCl, HNO₃, CH₃COOH, H₃PO₄), salt (ZnCl₂) and base (KOH). As a result, the phosphoric acid (H₃PO₄) demonstrated better catalytic activity than other chemical agents. The hydrolysis of NaBH₄ with the GAKS-catalyst (GAKS_cat) was studied depending on different parameters such as acid concentration, furnace burning temperature and time, catalyst amount, NaBH₄ concentration and hydrolysis reaction temperature. The obtained GAKS_cat was characterized by ICP-MS, elemental analysis, TGA, XRD, FT-IR, Boehm, TEM and SEM analyses and was evaluated for its catalytic activity in the hydrogen production from the hydrolysis reaction of NaBH₄. According to the results, the optimal H₃PO₄ percentage was found as 15%. The maximum hydrogen generation rate from the hydrolysis of NaBH₄ with the GAKS_cat was calculated as 20,199 mL min⁻¹ g_cat⁻¹. As a result, it can be said that GAKS treated with 15% H₃PO₄ as a catalyst for hydrogen production is an effective alternative due to its high hydrogen production rate.     

Optimisation of sepiolite clay with phosphoric acid treatment as support material for CoB catalyst and application to produce hydrogen from the NaBH4 hydrolysis

Herein, the CoB catalyst supported on the sepiolite clay treated with phosphoric acid was utilized to produce hydrogen from the NaBH₄ hydrolysis. In order to analyse the performance of the phosphoric acid treated sepiolite clay supported-CoB catalyst, the NaBH₄ concentration effect, phosphoric acid concentration effect, phosphoric acid impregnation time effect, CoB catalyst percentage effect, and temperature effect were studied. In addition, XRD, XPS, SEM, TEM, BET, and FTIR analysis were performed for characterization of Co–B catalyst supported on the acid-treated sepiolite. The completion time of this hydrolysis reaction with Co–B (20%) catalyst supported on the sepiolite treated by 5 M phosphoric acid was approximately 80 min, whereas the completion time of this hydrolysis reaction with acid-free sepiolite-supported Co–B (20%) catalyst was approximately 260 min. There is a five-fold increase in the maximum production rate. The maximum hydrogen production rates of this hydrolysis reaction at 30 and 60 °C were found as 1486 and 5025 ml min⁻¹g⁻¹_catalyst, respectively. Activation energy was found as 21.4 kJ/mol. This result indicates that the acid treatment on sepiolite is quite successful. The re-usability of NaBH₄ hydrolysis reaction by CoB catalyst supported on sepiolite treated phosphoric acid for successive five cycles of NaBH₄ at 30 °C was investigated.     

Synthesis and characterization of Ni-Mo2C particles supported over hydroxyapatite for potential application as a catalyst for hydrogen production

Ni-Mo₂C particles supported over hydroxyapatite were synthesized as potential catalysts to hydrogen production applications due their physiochemical properties observed in characterization results, this favorable for biomass gasification. Mo₂C particles doped with Ni were synthesized by temperature programmed reaction method at 900 °C under hydrogen reducing atmosphere. Hydroxyapatite support was obtained from thermal extraction of bovine bones, in a temperature range from 700 to 900 °C. Ni-Mo₂C impregnation over hydroxyapatite support was made by incipient humidity method. X-ray diffraction analysis determined crystallographic phases of β-Mo₂C, NiC and hydroxyapatite. Though, bone organic matter degradation was observed by X-ray diffraction and confirmed by Infrared Spectroscopy with Fourier Transform (FTIR) the final structure of hydroxyapatite was maintained. Finally, textural properties analysis of support showed an increase in porosity structure with the increment of temperature. β-Mo₂C and NiC were obtained with similar catalytic activity than noble metals, also nickel improves hydrocarbons bonds rupture. Hydroxyapatite showed high stability and porosity at elevated temperatures attributable to synthesis conditions.     

Evaluation of dilute acid and alkaline pretreatments,enzymatic hydrolysis and fermentation of napiergrass for fuel ethanol production

Napiergrass (Pennisetum purpureum Schum.) is a promising low cost raw material which does not compete with food prices, has attractive yields and an environmentally friendly farming. Dilute sulfuric acid pretreatment of napiergrass was effective to obtain high yields of sugars and low level of degradation by-products from hemicellulose. Detoxification with Ca(OH)₂ removed inhibitors but showed sugars loss. An ethanol concentration of 21 g/L after 176 h was found from the hydrolyzate using Pichia stipitis NBRC 10063 (fermentation efficiency 66%). An additional alkaline pretreatment applied to the solid fraction remaining from the diluted acid pretreatment improved the lignin removal. The highest cellulose hydrolysis values were found with the addition of β-glucosidase and PEG 6000. The simultaneous hydrolysis and fermentation of the cellulosic fraction with Saccharomyces cerevisiae, 10% (w/v) solid concentration, β-glucosidase and PEG 6000, showed the highest ethanol concentration (24 g/L), and cellulose hydrolysis values (81%). 162 L ethanol/t of dry napiergrass were produced (overall efficiency of 52%): 128 L/t from the cellulosic fraction and 34 L/t from the hemicellulosic fraction.