Hydrolysis Of Sweet Sorghum Bagasse Research Articles

Enhancing biomass conservation and enzymatic hydrolysis of sweet sorghum bagasse by combining pretreatment with ensiling and NaOH.

Lignocellulosic pretreatment is an important stage in biomass utilization, which usually requires high input. In this study, a low-cost method using combined ensiling and NaOH was developed for lignocellulosic pretreatment. Sweet sorghum bagasse (SSB) was ensiled for 21 days and then treated with diluted NaOH (0%, 1%, and 2%) for fermentation. The results showed that the application of Lactobacillus plantarum (L) reduced fermentation losses of the silages, mainly low water-soluble carbohydrate (WSC) and ammonia nitrogen loss. Meanwhile, the application of Lactobacillus plantarum and ensiling enzyme (LE) promoted lignocellulosic degradation, as evidenced by low neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin (ADL), and hemicellulosic (HC) contents. The dominant bacterial genera were Lactobacillus, uncultured_bacterium_f_Enterobacteriaceae, and Pantoea after silage, which corresponded to the higher lactic acid and acetic contents and lower pH. The reducing sugar yields of SSB increased after combined pretreatment of silage and NaOH and were further enhanced by the 2% NaOH application, as evidenced by the high reducing sugar yield and microstructure damage, especially in the L-2% NaOH group and the LE-2% NaOH group, in which the reducing sugar yields were 87.99 and 94.45%, respectively, compared with those of the no additive control (CK)-0 NaOH group. Therefore, this study provides an effective method for SSB pretreatment to enhance biomass conservation.

Morphological Characterization Of Rumen Protozoa Isolated From Sweet Sorghum Hydrolysis Using Carabao (Bubalus bubalis Linn) Rumen Fluid

This study was conducted to characterize the morphology of rumen protozoa isolated in the batch type hydrolysis of sweet sorghum using 1% fresh carabao rumen fluid with duration of 0, 3, 6, 9, 12 and 15 days of the novel process hydrolysis. Hydrolysis was conducted using 5% chopped sweet sorghum bagasse. Nitrogen content was augmented with 0.35 g urea per 750 ml effective volume with low speed agitation of fermentation bottle at least 20 minutes twice daily and incubated at room temperature. Characterization was limited to microscopic evaluation of the morphological features of protozoa that was stained with methylene blue formalin saline solution. Protozoon population of 2.61 x 10 4 cfu/ml at initial period had significantly lowered down at the 15 days hydrolysis to 0.62 x 104 cfu/ml. Evaluation of morphology for the types of protozoa at different durations showed the predominance of species types with different orientations of caudal spines, shapes of the macromolecules, size of the body, and presence of adoral ciliary zones were features of species types from genus Eodinium Entodinium of the family Ophryoscolecidae. Evaluation of the hydrolysis condition showed that duration had significant effect on the pH (P>0.05). Sweet sorghum hydrolysis has initial pH 7 that significantly declined to pH 5 at 15 days duration. The population of the protozoa in the rumen fluid hydrolysis was significantly affected by duration of the hydrolysis (P>0.05). Entodinium were isolated at all durations of the acidic hydrolysis of sweet sorghum bagasse using carabao rumen fluid. In conclusion, morphological characteristics of the rumen protozoan shows how diverse are the composition of rumen protozoa in the carabao rumen fluid hydrolysis. The presence of the rumen protozoa is a justification of the novel carabao rumen fluid hydrolysis conversion of lignocelluloses in sweet sorghum bagasse into soluble carbohydrates for bioethanol production. The information is vital for animal feed utilization and bioethanol production optimization.

Morphological Characterization of Rumen Protozoa Isolated from Sweet Sorghum Hydrolysis Using Carabao (Bubalus bubalis Linn) Rumen Fluid

This study was conducted to morphologically characterize rumen protozoa isolated in the batch type hydrolysis of sweet sorghum using 1% fresh carabao rumen fluid with duration of Day 0, 3, 6, 9, 12 and 15 days of the novel process hydrolysis. Hydrolysis was conducted using 5% chopped sweet sorghum bagasse. Nitrogen content was augmented using 0.35 g urea per 750 ml effective volume with low speed agitation of fermentation bottle at least 20 minutes twice daily and incubated at room temperature. Characterization was limited to microscopic evaluation of the morphological features of protozoa that was stained with methylene blue formalin saline solution. Initial population of 2.61 x 10 4 cfu/ml at DO had significantly lowest at 0.62 x 104 cfu/ml during the 15 days hydrolysis. Evaluation of morphology for the types of protozoa at different durations showed the predominance of species types with different orientations of caudal spines, shapes of the macromolecules and size of the body, adoral ciliary zones closely related to the features of species types from genus Entodinium of the family Ophryoscolecidae. Evaluation of the hydrolysis condition showed that duration had significant effect on the pH (P>0.05). Sweet sorghum hydrolysis pH 7 at D0 had significantly declined to pH 5 at 15 days duration. The population of the protozoa in the rumen fluid hydrolysis was significantly affected by duration of the hydrolysis (P>0.05). Entodinium were isolated at all durations of the acidic hydrolysis of sweet sorghum bagasse using carabao rumen fluid. In conclusion, the diversity in composition of rumen protozoa is a justification of the novel carabao rumen fluid hydrolysis potential as pre-treatment in the conversion of lignocelluloses in sweet sorghum bagasse into soluble carbohydrates for bioethanol production. The information is vital for animal feed utilization and bioethanol production optimization.

Design and performance of amphiphilic lignin derivatives in enzymatic hydrolysis of sweet sorghum bagasse for bioethanol production

Sweet sorghum bagasse (SSB) is potential feedstock for bioethanol production due to its natural abundance and high cellulose content (> 40%). This work compared the impact of three variables relative to the enzymatic hydrolysis of SSB kraft pulp. The three variables were the biosurfactant from lignin derivative known as amphiphilic lignin derivatives (A-LD), the enzyme loading level, and the hydrolysis time. These variables were optimized by response surface methodology (RSM) with a Box-Behnken design (BBD). The concentration of polyethylene glycol (PEG) 4000 was also optimized to compare it with the A-LD performance in the enzymatic hydrolysis process. After optimization, the A-LD produced a higher reducing sugar yield (RSY) (99.45%) than the PEG 4000. The difference in the predicted versus experimental values of the RSY was less than 4%, which means that the model was highly predictive. The adequacy of the model was confirmed by a regression value close to 1 for the A-LD assisted test. The result implies that the A-LD significantly improved the enzymatic hydrolysis performance to enhance the RSY. Moreover, the BBD is adequate and useful to identify the optimum concentration of surfactant.

Microwave and steam mediated alkaline pretreatments of sweet sorghum bagasse: Study of the energy efficiency

The effects of microwave and steam mediated pretreatments were evaluated and compared relative to the hydrolysis of sweet sorghum bagasse (SSB) in the presence of sodium hydroxide. The results established the optimum parameters for energy consumption and sugar production after hydrolysis of the pretreated SSB. The energy balance was better in microwave treatment compared with the steam treatment. The results recommended pretreatment at 300 watts power setting in the microwave oven up to 10 min. At higher wattage setting and longer exposure time, increased sugar yields were obtained, although the efficiency of the process decreased when the energy balance was calculated. The energy balance was calculated as the proportion of energy consumed during the pretreatments to the energy that can be produced by fermenting released glucose to ethanol. In this study, the energy consumed during the different pretreatments varied from 1/33 to 1/200 of the energy obtainable by fermenting released glucose to ethanol. Overall, the pretreatment of SSB to produce fermentable sugars was effective, and the energy balance was positive both in microwave and steam pretreatments of alkaline suspension of SSB. In microwave treatment the energy applied can be more accurately dosed, and consequently the energy balance was improved compared to steam treatment.

Xylanase production from Penicillium citrinum isolate HZN13 using response surface methodology and characterization of immobilized xylanase on glutaraldehyde-activated calcium-alginate beads.

The present study reports the production of high-level cellulase-free xylanase from Penicillium citrinum isolate HZN13. The variability in xylanase titers was assessed under both solid-state (SSF) and submerged (SmF) fermentation. SSF was initially optimized with different agro-waste residues, among them sweet sorghum bagasse was found to be the best substrate that favored maximum xylanase production (9643 U/g). Plackett–Burman and response surface methodology employing central composite design were used to optimize the process parameters for the production of xylanase under SSF. A second-order quadratic model and response surface method revealed the optimum conditions for xylanase production (sweet sorghum bagasse 25 g/50 ml; ammonium sulphate 0.36 %; yeast extract 0.6 %; pH 4; temperature 40 °C) yielding 30,144 U/g. Analysis of variance (ANOVA) showed a high correlation coefficient (R 2 = 97.63 %). Glutaraldehyde-activated calcium-alginate-immobilized purified xylanase showed recycling stability (87 %) up to seven cycles. Immobilized purified xylanase showed enhanced thermo-stability in comparison to immobilized crude xylanase. Immobilization kinetics of crude and purified xylanase revealed an increase in K m (12.5 and 11.11 mg/ml) and V max (12,500 and 10,000 U/mg), respectively. Immobilized (crude) enzymatic hydrolysis of sweet sorghum bagasse released 8.1 g/g (48 h) of reducing sugars. Xylose and other oligosaccharides produced during hydrolysis were detected by High-Performance Liquid Chromatography. The biomass was characterized by Scanning Electron Microscopy, Energy Dispersive X-ray and Fourier Transformation Infrared Spectroscopy. However, this is one of the few reports on high-level cellulase-free xylanase from P. citrinum isolate using sweet sorghum bagasse.Electronic supplementary materialThe online version of this article (doi:10.1007/s13205-016-0484-9) contains supplementary material, which is available to authorized users.

Optimization of Hydrolysis Process to Obtain Fermentable Sugars from Sweet Sorghum Bagasse Using a Box–Behnken Design

Sweet sorghum (Sorghum bicolor (L.) Moench) bagasse is a lignocellulosic material consisting mainly of hemicellulose and cellulose, a potential source of fermentable sugars. The present study aimed to optimize the hydrolysis of sweet sorghum bagasse to obtain the highest concentrations of xylose and glucose with the minimum amount of inhibitor compounds. Seven varieties of sweet sorghum bagasse were used for the hydrolysis experiment, carried out in three stages with a 23 Box–Behnken factorial design; the critical factors selected for both stages were H2SO4 and H2O2 concentrations, time and liquid–solid ratio (LSR). The alkaline hydrolysis was carried out with a subsequent enzymatic hydrolysis using 0.4 mL cellulose and 0.5 mL beta-glucosidase. The optimum conditions for acid hydrolysis were H2SO4 (1.375 % w/v), time (36 min) and LSR (4.9:1 v/w of bagasse) resulting in values of 11.55 g/L glucose and 41.27 g/L xylose, respectively; for alkaline hydrolysis H2O2 (4.5 % w/v), time (45 h) and LSR (16:1 v/w of bagasse) were the optimum values. Under these conditions, 65.96 g/L glucose concentration was obtained. Validation of the model indicated no difference between predicted and observed values in the optimization of the hydrolysis process.

Laboratory scale optimization of alkali pretreatment for improving enzymatic hydrolysis of sweet sorghum bagasse

Sweet sorghum has been identified as a promising feedstock for biological conversion to fuels as well as other chemicals. The lignocellulosic stalk of sweet sorghum, called sweet sorghum bagasse (SSB) is a potential source of lignocellulosic biofuel. The primary goal of this study was to determine optimal alkali (lime: Ca(OH)2 and lye: NaOH) pretreatment conditions to obtain higher yield of total reducing sugar while reducing the lignin content for biofuel production from SSB. Biomass conversion and lignin removal were simultaneously optimized through four quadratic models analyzed by response surface methodology (RSM). The optimal conditions for lime pretreatment was 1.7% (w/v) lime concentration, 6.0% (w/v) SSB loading, 2.4h pretreatment time with predicted yields of 85.6 total biomass conversion and 35.5% lignin reduction. For lye pretreatment, 2% (w/v) alkali, 6.8% SSB loading and 2.3h duration were the optimal levels with predicted biomass conversion and lignin reduction of 92.9% and 50.0%, respectively. More intensive pretreatment conditions removed higher amounts of hemicelluloses and cellulose. Fourier transform infrared spectroscopy (FTIR) spectrum and scanning electron microscope (SEM) image revealed compositional and microstructural changes caused by the alkali pretreatment.

Multi-component thermostable cellulolytic enzyme production by Aspergillus niger HN-1 using pea pod waste: Appraisal of hydrolytic potential with lignocellulosic biomass

Solid state fermentation with pea pod waste and Aspergillus niger HN-1 resulted in filter paper cellulase (FP) and β-glucosidase (BGL) activity of 30FPU/gds and 270U/gds, respectively. Validation with the response surface optimized parameters (moisture content: 65%, pH 6.0, temperature: 33°C, time: 84h) in a solid-state tray fermentation enhanced FP and BGL activity by about 40 and 28%, respectively. Multi-component enzyme from A. niger HN-1 produced FP, BGL, endoglucanase (EG), cellobiohydrolase (CBHI), xylanase, α-l-arabinofuranosidase, β-xylosidase and xylan esterase with activities of 41.07±2.11FPU/gds, 345.69±17.1, 480.3±21.5, 52.1±1.5, 2800.5±88.4, 88.1±9.3, 280.8±11.4 and 3321.7±14.8U/gds, respectively. Enzyme was optimally active at temperature and pH of 55°C and 5.0, respectively and demonstrated thermostability by retaining >95% activity for 6h at 55°C. SDS-PAGE showed the presence of 11 protein bands with molecular mass ranging between 20 and 200kDa, while zymogram revealed the presence of multiple forms of EG, CBH and BGL with varying molecular mass. Hydrolysis of sweet sorghum bagasse at relatively high substrate loading (15%, w/v) with crude enzyme at 20FPU/gds in thermostatically controlled glass reactor led to conversion of 82–91% of holocellulose to fermentable sugars in just 24h as evident from HPLC analysis, showing promise for the reported enzyme in bioprocessing applications.

A novel cost-effective technology to convert sucrose and homocelluloses in sweet sorghum stalks into ethanol

BackgroundSweet sorghum is regarded as a very promising energy crop for ethanol production because it not only supplies grain and sugar, but also offers lignocellulosic resource. Cost-competitive ethanol production requires bioconversion of all carbohydrates in stalks including of both sucrose and lignocellulose hydrolyzed into fermentable sugars. However, it is still a main challenge to reduce ethanol production cost and improve feasibility of industrial application. An integration of the different operations within the whole process is a potential solution.ResultsAn integrated process combined advanced solid-state fermentation technology (ASSF) and alkaline pretreatment was presented in this work. Soluble sugars in sweet sorghum stalks were firstly converted into ethanol by ASSF using crushed stalks directly. Then, the operation combining ethanol distillation and alkaline pretreatment was performed in one distillation-reactor simultaneously. The corresponding investigation indicated that the addition of alkali did not affect the ethanol recovery. The effect of three alkalis, NaOH, KOH and Ca(OH)2 on pretreatment were investigated. The results indicated the delignification of lignocellulose by NaOH and KOH was more significant than that by Ca(OH)2, and the highest removal of xylan was caused by NaOH. Moreover, an optimized alkali loading of 10% (w/w DM) NaOH was determined. Under this favorable pretreatment condition, enzymatic hydrolysis of sweet sorghum bagasse following pretreatment was investigated. 92.0% of glucan and 53.3% of xylan conversion were obtained at enzyme loading of 10 FPU/g glucan. The fermentation of hydrolyzed slurry was performed using an engineered stain, Zymomonas mobilis TSH-01. A mass balance of the overall process was calculated, and 91.9 kg was achieved from one tonne of fresh sweet sorghum stalk.ConclusionsA low energy-consumption integrated technology for ethanol production from sweet sorghum stalks was presented in this work. Energy consumption for raw materials preparation and pretreatment were reduced or avoided in our process. Based on this technology, the recalcitrance of lignocellulose was destructed via a cost-efficient process and all sugars in sweet sorghum stalks lignocellulose were hydrolysed into fermentable sugars. Bioconversion of fermentable sugars released from sweet sorghum bagasse into different products except ethanol, such as butanol, biogas, and chemicals was feasible to operate under low energy-consumption conditions.

Low severity dilute-acid hydrolysis of sweet sorghum bagasse

Sweet sorghum is emerging as a promising energy crop in India, with potential for ethanol production both from the extracted juice and the bagasse residue. This work investigates the release of fermentable total sugars (TS) and formation of total degradation compounds (TDC) by dilute sulphuric acid hydrolysis of sweet sorghum bagasse from the genotype SSV 84. Hydrolysis was conducted at moderate temperatures (100°C and 121°C). The effect of pretreatment severity (measured by the combined severity factor, CS), particle size and substrate loading on the hydrolysate composition was examined. The kinetics of xylose, acetic acid and furfural formation was also studied. The maximum theoretical yield is 29.9g C5 sugars/100g bagasse on dry weight basis. Under the conditions of this study, 10% substrate loading in the CS range of 1.64–1.93 was optimal with C5 yield >22.3g/100g bagasse and efficiency (TS/TDC ratio) >8. Bagasse particle size reduction also resulted in a higher efficiency. SEM and FT-IR analysis of the solid residue confirmed disruption of the biomass structure and removal of functional groups associated with hemicelluloses and lignin. This study demonstrates that acid hydrolysis at moderate temperature has an advantage in terms of high sugars concentration vis-a-vis low degradation compounds formation.

Kinetic model analysis of dilute sulfuric acid-catalyzed hemicellulose hydrolysis in sweet sorghum bagasse for xylose production

Sweet sorghum is a high-yielding energy crop that leaves a large amount of lignocellulosic residues after the sugar fraction fermented to ethanol. Here, we developed a biphasic kinetic model for the dilute sulfuric acid-catalyzed hemicellulose hydrolysis of sweet sorghum bagasse at temperatures of 110–150°C, and we then calculated the kinetic parameters for xylose production and furfural decomposition. The results indicated that elevated reaction temperatures promote the hydrolysis of hemicellulose and the degradation of xylose. The xylose yield increased in proportion to reaction time in the initial stages and then declined due to the degradation of xylose to furfural. The pre-exponential factors for the ‘easy-to-hydrolyze’ fraction, the ‘hard-to-hydrolyze’ fraction of hemicellulose and xylose degradation were 3.53×106, 1.80×105 and 0.62min−1, respectively, and the activation energies were 60.7, 58.1 and 14.5kJ/mol, respectively. The ideal hydrolysis condition for xylose production was 140°C for 50min, under which the xylose yield reached 60% of hemicellulose weight. This xylose can be used to form bioethanol and produce further downstream products.

Relatively High-Substrate Consistency Hydrolysis of Steam-Pretreated Sweet Sorghum Bagasse at Relatively Low Cellulase Loading

Sweet sorghum bagasse (SSB) was steam pretreated in the conditions of 190 °C for 5 min to assess its amenability to the pretreatment and enzymatic hydrolysis. Results showed that pretreatment conditions were robust enough to pretreat SSB with maximum of 87% glucan and 72% xylan recovery. Subsequent enzymatic hydrolysis showed that the pretreated SSB at 2% substrate consistency resulted in maximum of 70% glucan-glucose conversion. Increasing substrate consistency from 2% to 16% led to a significant reduction in glucan conversion. However, the decrease ratio of glucan-glucose conversion was the minimum when the consistency increased from 2% to 12%. When the pretreated SSB consistency of 12% was applied for hydrolysis, increase in cellulase loading from 7.5 up to 20 filter paper units (FPU)/g glucan resulted only in 14% increase in glucan-glucose conversion compared to 20% increase with cellulase loading varying from 2.5 to 7.5 FPU/g glucan. More than 10 cellobiase units (CBU)/g glucan β-glucosidase supplementation had no noticeable improvement on glucan-glucose conversion. Additionally, supplementation of xylanase was found to significantly increase glucan-glucose conversion from 50% to 80% with the substrate consistency of 12%, when the cellulase and β-glucosidase loadings were at relatively low enzyme loadings (7.5 FPU/g and 10 CBU/g glucan). It appeared that residual xylan played a critical role in hindering the ease of hydrolysis of SSB. A proper xylanase addition was suggested to achieve a high hydrolysis yield at relatively high substrate consistency with relatively low enzyme loadings.

The effects of four different pretreatments on enzymatic hydrolysis of sweet sorghum bagasse

Four pretreatment processes including ionic liquids, steam explosion, lime, and dilute acid were used for enzymatic hydrolysis of sweet sorghum bagasse. Compared with the other three pretreatment approaches, steam-explosion pretreatment showed the greatest improvement on enzymatic hydrolysis of the bagasse. The maximum conversion of cellulose and the concentration of glucose obtained from enzymatic hydrolysis of steam explosion bagasse reached 70% and 25 g/L, respectively, which were both 2.5 times higher than those of the control (27% and 11 g/L). The results based on the analysis of SEM photos, FTIR, XRD and NMR detection suggested that both the reduction of crystallite size of cellulose and cellulose degradation from the Iα and Iβ to the Fibril surface cellulose and amorphous cellulose were critical for enzymatic hydrolysis. These pretreatments disrupted the crystal structure of cellulose and increased the available surface area, which made the cellulose better accessible for enzymatic hydrolysis.