Efficient conversion of sugarcane stalks into ethanol employing low temperature alkali pretreatment method

An alternative route for bio-ethanol production from sugarcane stalks (juice and bagasse) featuring a previously reported low temperature alkali pretreatment method was evaluated. Test-tube scale pretreatment-saccharification experiments were carried out to determine optimal LTA pretreatment conditions for sugarcane bagasse with regard to the efficiency of enzymatic hydrolysis of the cellulose. Free fermentable sugars and bagasse recovered from 2 kg of sugarcane stalks were jointly converted into ethanol via separate enzymatic hydrolysis and fermentation (SHF). Results showed that 98% of the cellulose present in the optimally pretreated bagasse was hydrolyzed into glucose after 72-h enzymatic saccharification using commercially available cellulase and β-glucosidase preparations at relatively low enzyme loading. The fermentable sugars in the mixture of the sugar juice and the bagasse hydrolysate were readily converted into 193.5 mL of ethanol by Saccharomyces cerevisiae within 12h, achieving 88% of the theoretical yield from the sugars and cellulose.     

A strain of <Emphasis Type="Italic">Meyerozyma guilliermondii</Emphasis> isolated from sugarcane juice is able to grow and ferment pentoses in synthetic and bagasse hydrolysate media

The search for new microbial strains that are able to withstand inhibitors released from hemicellulosic hydrolysis and are also still able to convert sugars in ethanol/xylitol is highly desirable. A yeast strain isolated from sugarcane juice and identified as Meyerozyma guilliermondii was evaluated for the ability to grow and ferment pentoses in synthetic media and in sugarcane bagasse hydrolysate. The yeast grew in xylose, arabinose and glucose at the same rate at an initial medium pH of 5.5. At pH 4.5, the yeast grew more slowly in arabinose. There was no sugar exhaustion within 60 h. At higher xylose concentrations with a higher initial cell concentration, sugar was exhausted within 96 h at pH 4.5. An increase of 350 % in biomass was obtained in detoxified hydrolysates, whereas supplementation with 3 g/L yeast extract increased biomass production by approximately 40 %. Ethanol and xylitol were produced more significantly in supplemented hydrolysates regardless of detoxification. Xylose consumption was enhanced in supplemented hydrolysates and arabinose was consumed only when xylose and glucose were no longer available. Supplementation had a greater impact on ethanol yield and productivity than detoxification; however, the product yields obtained in the present study are still much lower when compared to other yeast species in bagasse hydrolysate. By the other hand, the fermentation of both xylose and arabinose and capability of withstanding inhibitors are important characteristics of the strain assayed.     

Optimization of amylase production by Aspergillus niger in solid-state fermentation using sugarcane bagasse as solid support material

Synthesis of amylase by Aspergillus niger strain UO-01 under solid-state fermentation with sugarcane bagasse was optimized by using response surface methodology and empirical modelling. The process parameters tested were particle size of sugarcane bagasse, incubation temperature and pH, moisture level of solid support material and the concentrations of inoculum, total sugars, nitrogen and phosphorous. The optimum conditions for high amylase production (457.82 EU/g of dry support) were particle size of bagasse in the range of 6–8 mm, incubation temperature and pH: 30.2°C and 6.0, moisture content of bagasse: 75.3%, inoculum concentration: 1 × 10⁷ spores/g of dry support and concentrations of starch, yeast extract and KH₂PO₄: 70.5, 11.59 and 9.83 mg/g of dry support, respectively. After optimization, enzyme production was assayed at the optimized conditions. The results obtained corroborate the effectiveness and reliability of the empirical models obtained.     

Suitability of some local agro-industrial wastes as carrier materials for cyanobacterial inoculant

Survival and nitrogenase efficiency ofNostoc commune andN. austinii were evaluated monthly in four carrier materials (sugarcane bagasse, wheat straw, wheat bran and peat) at 10, 30 and 40 °C. Survival, as well as nitrogenase activity, of both species was much better in peat, followed by wheat bran, sugarcane bagasse than in wheat straw at 10 and 30 °C up to three months, the activity ofN. commune being better thanN. austinii. None of the materials tested was found to be superior to peat as carrier ofNostoc species but the results indicated that wheat bran and sugarcane bagasse can be used as inoculant carriers with relative success. Storage of inoculants in these carriers is feasible at 30 °C up to three months.     

Production of bioactive polysaccharides by Inonotus obliquus under submerged fermentation supplemented with lignocellulosic biomass and their antioxidant activity

The effect of lignocellulose degradation in wheat straw, rice straw, and sugarcane bagasse on the accumulation and antioxidant activity of extra- (EPS) and intracellular polysaccharides (IPS) of Inonotus obliquus under submerged fermentation were first evaluated. The wheat straw, rice straw, and sugarcane bagasse increased the EPS accumulation by 91.4, 78.6, and 74.3 % compared with control, respectively. The EPS and IPS extracts from the three lignocellulose media had significantly higher hydroxyl radical- and 2,2-diphenyl-1-picrylhydrazyl radical-scavenging activity than those from the control medium. Of the three materials, wheat straw was the most effective lignocellulose in enhancing the mycelia growth, accumulation and antioxidant activity of I. obliquus polysaccharides (PS). The carbohydrate and protein content, as well as the monosaccharide compositions of the EPS and IPS extracts, were correlated with sugar compositions and dynamic contents during fermentation of individual lignocellulosic materials. The enhanced accumulation of bioactive PS of cultured I. obliquus supplemented with rice straw, wheat straw, and bagasse was evident.     

Biological detoxification of different hemicellulosic hydrolysates using Issatchenkia occidentalis CCTCC M 206097 yeast

This work had as its main objective to contribute to the development of a biological detoxification of hemicellulose hydrolysates obtained from different biomass plants using Issatchenkia occidentalis CCTCC M 206097 yeast. Tests with hemicellulosic hydrolysate of sugarcane bagasse in different concentrations were carried out to evaluate the influence of the hydrolysate concentration on the inhibitory compounds removal from the sugarcane bagasse hydrolysate, without reduction of sugar concentration. The highest reduction values of inhibitors concentration and less sugar losses were observed when the fivefold concentrated hydrolysate was treated by the evaluated yeast. In these experiments it was found that the high sugar concentrations favored lower sugar consumption by the yeast. The highest concentration reduction of syringaldehyde (66.67%), ferulic acid (73.33%), furfural (62%), and 5-HMF (85%) was observed when the concentrated hydrolysate was detoxified by using this yeast strain after 24 h of experimentation. The results obtained in this work showed the potential of the yeast Issatchenkia occidentalis CCTCC M 206097 as detoxification agent of hemicellulosic hydrolysate of different biomass plants.     

四种添加物对铁皮石斛原球茎生长及多糖含量的影响

为探讨铁皮石斛(Dendrobium officinale)培养基中添加物的作用,在1/2MS培养基中加入椰肉、甘蔗渣、香蕉皮和麦麸等4种添加物,研究不同浓度添加物和培养时间对原球茎生长和多糖含量的影响。结果表明,4种添加物对铁皮石斛原球茎的增殖、分化和多糖含量均有一定影响,其中添加15.0 g L–1甘蔗渣,培养60 d能明显促进铁皮石斛原球茎的增殖与分化(146.1%);而添加20.0 g L–1甘蔗渣,培养40 d能显著提高铁皮石斛原球茎多糖含量(50.4%)。这说明甘蔗渣是培养铁皮石斛原球茎的适宜添加物,既能促进铁皮石斛原球茎的生长发育,还能降低生产成本。     

Screening and Characterization of the High-Cellulase-Producing Strain Aspergillus glaucus XC9

Cellulose is a kind of renewable resource that is abundant in nature.It can be degraded by microorganisms such as mildew.A mildew strain with high cellulase activity was isolated from mildewy maize cob and classified as Aspergillus glaucus XC9 by morphological and 18S rRNA gene sequence analyses.We studied the effects of nitrogen source,initial pH,temperature,incubation time,medium composition,and surfactants on cellulase production.Maximal activities of carboxymethylcellulase (6,812 U/g dry koji) and filter paperase (172 U/g dry koji) were obtained in conditions as follows:initial pH,5.5-6.0;temperature,30℃;cultivation period,3-4 days;inoculum ratio,6% (vol/vol);sugarcane bagasse/wheat bran ratio,4:6.When bagasse was used as substrate and mixed with wet koji at a 1:1 (wt/wt) ratio,the yield of reducing sugars was 36.4%.The corresponding conversion rate of cellulose to reducing sugars went as high as 81.9%.The results suggest that A.glaucus XC9 is a preferred candidate for cellulase production.     

Integrated Strategies to Enhance Cellulolytic Enzyme Production Using an Instrumented Bioreactor for Solid-State Fermentation of Sugarcane Bagasse

The conversion of agro-industrial residues, such as sugarcane bagasse, into high-value products and renewable energy, within the biorefinery concept, is a potential alternative towards the sustainable management of these resources. This work evaluates the production of cellulolytic enzymes by a selected strain of Aspergillus niger cultivated in sugarcane bagasse under solid-state fermentation using an instrumented lab-scale bioreactor. The effects of environmental factors including the type of substrate and medium composition, as well as the operational conditions (air flow rate, inlet air relative humidity, and initial substrate moisture content) on the production of the enzymatic complex were evaluated using statistical design tools. Significant increases in FPase, endoglucanase, and xylanase activities were achieved under the optimized conditions predicted by the models, with values of 0.88, 21.77, and 143.85 IU/g of dry solid substrate, respectively, representing around ten-, four-, and twofold increases compared to the activities obtained under the initial growth conditions. This demonstrates the importance of evaluating environmental and operational criteria in order to achieve efficient enzyme production. The crude enzymatic extract obtained under optimized conditions was employed for enzymatic hydrolysis of pretreated sugarcane bagasse. Approximately 13 % of total reducing sugars, and a glucose concentration of 2.54 g/L, were obtained after 22 h of hydrolysis of steam exploded sugarcane bagasse, indicating that the enzymatic cocktail produced has good potential for use in the conversion of biomass.     

Enhancement of <Emphasis Type="Italic">Penicillium echinulatum</Emphasis> glycoside hydrolase enzyme complex

The enhancement of enzyme complex produced by Penicillium echinulatum grown in several culture media components (bagasse sugarcane pretreated by various methods, soybean meal, wheat bran, sucrose, and yeast extract) was studied to increment FPase, xylanase, pectinase, and β-glucosidase enzyme activities. The present results indicated that culture media composed with 10 g/L of the various bagasse pretreatment methods did not have any substantial influence with respect to the FPase, xylanase, and β-glucosidase attained maximum values of, respectively, 2.68 FPU/mL, 2.04, and 115.4 IU/mL. On the other hand, proposed culture media to enhance β-glucosidase production composed of 10 g/L steam-exploded bagasse supplemented with soybean flour 5.0 g/L, yeast extract 1.0 g/L, and sucrose 10.0 g/L attained, respectively, 3.19 FPU/mL and 3.06 IU/mL while xylanase was maintained at the same level. The proteomes obtained from the optimized culture media for enhanced FPase, xylanase, pectinase, and β-glucosidase production were analyzed using mass spectrometry and a panel of GH enzyme activities against 16 different substrates. Culture medium designed to enhance β-glucosidase activity achieved higher enzymatic activities values (13 measured activities), compared to the culture media for FPase/pectinase (9 measured activities) and xylanase (7 measured activities), when tested against the 16 substrates. Mass spectrometry analyses of secretome showed a consistent result and the greatest number of spectral counts of Cazy family enzymes was found in designed β-glucosidase culture medium, followed by FPase/pectinase and xylanase. Most of the Cazy identified protein was cellobiohydrolase (GH6 and GH7), endoglucanase (GH5), and endo-1,4-β-xylanase (GH10). Enzymatic hydrolysis of hydrothermally pretreated sugarcane bagasse performed with β-glucosidase enhanced cocktail achieved 51.4 % glucose yield with 10 % w/v insoluble solids at enzyme load of 15 FPU/g material. Collectively the results demonstrated that it was possible to rationally modulate the GH activity of the enzymatic complex secreted by P. echinulatum using adjustment of the culture medium composition. The proposed strategy may contribute to increase enzymatic hydrolysis of lignocellulosic materials.     

Comparative hydrolysis and fermentation of sugarcane and agave bagasse

Sugarcane and agave bagasse samples were hydrolyzed with either mineral acids (HCl), commercial glucanases or a combined treatment consisting of alkaline delignification followed by enzymatic hydrolysis. Acid hydrolysis of sugar cane bagasse yielded a higher level of reducing sugars (37.21% for depithed bagasse and 35.37% for pith bagasse), when compared to metzal or metzontete (agave pinecone and leaves, 5.02% and 9.91%, respectively). An optimized enzyme formulation was used to process sugar cane bagasse, which contained Celluclast, Novozyme and Viscozyme L. From alkaline–enzymatic hydrolysis of sugarcane bagasse samples, a reduced level of reducing sugar yield was obtained (11–20%) compared to agave bagasse (12–58%). Selected hydrolyzates were fermented with a non-recombinant strain of Saccharomyces cerevisiae. Maximum alcohol yield by fermentation (32.6%) was obtained from the hydrolyzate of sugarcane depithed bagasse. Hydrolyzed agave waste residues provide an increased glucose decreased xylose product useful for biotechnological conversion.     

Invertase activity of intact cells of Saccharomyces cerevisiae growing on sugarcane molasses. II. Unsteady-state continuous-culture tests

During unsteady-state continuous culture of Saccharomyces cerevisiae on sugarcane blackstrap molasses, the invertase activity of the intact yeast cells oscillated. Disturbances were produced by changing medium composition, air rate, impeller speed, and dilution rate. The influence of the oxygen supply rate and of the dilution rate on the invertase activity depend on the medium composition. The highest invertase activity was obtained when, after a steady-state attained using unsupplemented culture medium, nutrients were added to the feeding mash. A Monod-like equation seems to be the best representation of the correlation between the specific rate of reducing sugars consumption and the specific rate of nonreducing sugar hydrolysis by the yeast cells.     

Comparative efficiency of wheat straw and sugarcane bagasse biochar reduces the cadmium bioavailability to spinach and enhances the microbial activity in contaminated soil

Abstract

Biochar is considered a novel soil amendment for cadmium (Cd) stabilization in contaminated soils. A pot experiment was conducted to examine the efficiency of wheat straw and sugarcane bagasse induced biochar on Cd mobility in soil and its bioavailability to spinach in contaminated soil. Soil pH, Cd contents in plant tissues and microbial biomass were examined. Results showed that Cd was significantly decreased by 30.95% and 20.83% with wheat straw and sugarcane bagasse biochar at 2% application rate respectively, relative to the control. Similarly, Cd contents were decreased in plants shoots by 15.41 and 14.33%, while in roots by 48.3 and 35.54%, when wheat straw and sugarcane biochar were added at 2% application rate respectively. Moreover, soil microbial biomass was significantly increased with the application of all biochar types and their applications rates. Finally, wheat straw biochar at 2% application rate can be considered as an effective approach for Cd stabilization in contaminated soils.     

Xylitol production from corn fiber and sugarcane bagasse hydrolysates by Candida tropicalis

A natural isolate, Candida tropicalis was tested for xylitol production from corn fiber and sugarcane bagasse hydrolysates. Fermentation of corn fiber and sugarcane bagasse hydrolysate showed xylose uptake and xylitol production, though these were very low, even after hydrolysate neutralization and treatments with activated charcoal and ion exchange resins. Initial xylitol production was found to be 0.43 g/g and 0.45 g/g of xylose utilised with corn fiber and sugarcane bagasse hydrolysate respectively. One of the critical factors for low xylitol production was the presence of inhibitors in these hydrolysates. To simulate influence of hemicellulosic sugar composition on xylitol yield, three different combinations of mixed sugar control experiments, without the presence of any inhibitors, have been performed and the strain produced 0.63 g/g, 0.68 g/g and 0.72 g/g of xylose respectively. To improve yeast growth and xylitol production with these hydrolysates, which contain inhibitors, the cells were adapted by sub culturing in the hydrolysate containing medium for 25 cycles. After adaptation the organism produced more xylitol 0.58 g/g and 0.65 g/g of xylose with corn fiber hydrolysate and sugarcane bagasse hydrolysate respectively.     

Do wood-based panels made with agro-industrial residues provide environmentally benign alternatives? An LCA case study of sugarcane bagasse addition to particle board manufacturing

Purpose

Sugarcane bagasse is one of the main agro-industrial residues which can be used to produce wood-based panels. However, more investigations related to its environmental performance assessment are needed, focusing on questions such as: Does it provide environmental benefits? What are its main environmental impacts? Could it substitute wood as raw material? Accordingly, this paper presents a life cycle assessment (LCA) study of particle board manufactured with sugarcane bagasse residues.

Methods

The cradle-to-gate assessment of 1 m³ of particle board made with sugarcane bagasse (PSB) considered three main subsystems: bagasse generation, bagasse distribution, and PSB production. For the inventory of PSB, dataset from two previous LCA studies related to the conventional particle board production and the ethanol life cycle for the Brazilian context were used. The allocation criterion for the bagasse generation subsystem was 9.08 % (economic base). The potential environmental impact phase was assessed by applying the CML and USEtox methods. PSB was compared with the conventional particle board manufactured in Brazil by the categories of the CML and USETox, and including land use indicators. Finally, two scenarios were analyzed to evaluate the influence of the allocation criteria and the consumption of sugarcane bagasse.

Results and discussion

All hotspots identified by CML and USETox methods are mainly related to the PSB production subsystem (24–100 % of impacts) due to heavy fuel oil, electricity, and urea-formaldehyde resin supply chain. The bagasse generation subsystem was more relevant to the eutrophication category (75 % of impacts). The bagasse distribution subsystem was not relevant because the impacts on all categories were lower than 1 %. PSB can substitute the conventional particle board mainly because of its lower contribution to abiotic depletion and ecotoxicity. Regarding land use impacts, PSB showed lower values according to all indicators (38–40 % of all impacts), which is explained by the lower demand for land occupation in comparison to that of the traditional particle board.

Conclusions

PSB can replace the traditional particle board due to its better environmental performance. The analysis of the economic allocation criterion was relevant only for the EP category, being important to reduce diesel and N-based fertilizers use during sugarcane cultivation. Regarding the influence of the sugarcane bagasse consumption, it is suggested that the sugarcane bagasse be mixed up to 75 % during particle board manufacturing so that good quality properties and environmental performance of panels can be provided.     

Comparison of pretreatment strategies of sugarcane baggase: experimental design for citric acid production

Solid state fermentation was carried out to compare efficiency of acid, alkaline and urea pretreatment of sugarcane bagasse for production of citric acid using Aspergillus niger ATCC 9142. Plackett-Burman statistical design was used to evaluate significance of variables. Pretreatment of bagasse by urea was known as the most influential treatment to increase citric acid production (137.6g/kg of dry sugarcane bagasse and citric acid yield of 96% based on sugar consumed). Finally, up scaling was achieved to a 20L solid state fermentor in which humidity was constant in gas phase and urea-treated sugarcane bagasse. The produced acid concentration and yield in fermentor was 82.38g/kg of dry substrate and 26.45g/kgday, respectively.     

Enhanced enzymatic hydrolysis of sugarcane bagasse by N-methylmorpholine-N-oxide pretreatment

The cellulose dissolution solvent used in Lyocell process for cellulose fiber preparation, N-methylmorpholine-N-oxide (NMMO) monohydrate, was demonstrated to be an effective agent for sugarcane bagasse pretreatment. Bagasse of 20wt% was readily dissolved in NMMO monohydrate at 130 degrees C within 1h. After dissolution, bagasse could be regenerated by rapid precipitation with water as a porous and amorphous mixture of its original components. The regenerated bagasse exhibited a significant enhancement on enzymatic hydrolysis kinetic. Not only the reducing sugars releasing rate but also hydrolysis yield was enhanced at least twofold as compared with that of untreated bagasse. The cellulose fraction of regenerated bagasse was nearly hydrolyzed to glucose after 72h hydrolysis with Cellulase AP3. The recycled NMMO demonstrated the same performance as the fresh one on bagasse pretreatment for hydrolysis enhancement. The regenerated bagasse was directly used in simultaneous saccharification and fermentation (SSF) for ethanol production by Zymomonas mobilis. No negative effect on ethanol fermentation was observed and ethanol yield approximately 0.15 g ethanol/g baggasse was achieved.     

White-rot fungal growth on sugarcane lignocellulosic residue

Summary Twelve white-rot fungi were grown in solid state culture on sugarcane chips previously fermented by yeast employing the EX-FERM process. The lignocellulosic sugarcane residue had 12.5% permanganate lignin and 81.3% holocellulose. After 5 to 6 weeks at 20° C, all fungi produced a solid residue which had a lower in vitro dry matter enzymatic digestibility than the original bagasse, with the exception of Coriolus versicolor which showed a slight increase of 0.6 units. Four fungi produced a residue with higher soluble solids than the original sample. Lignin losses were rather similar for all fungi tested, an average value of 38.64% of the original value was obtained. About the same amount of hemicellulose was degreaded, 32.22%. Most fungi showed a preference for hemicellulose hydrolysis over cellulose degradation. The two fungi that showed greater cellulolytic activity were Sporotrichum pulverulentum and Dichomitus squalens. No appreciable dry matter losses were detected for Agrocybe aergerita and Flammulina velutipes.     

Optimization of steam explosion as a method for increasing susceptibility of sugarcane bagasse to enzymatic saccharification

The technique of autohydrolysis steam explosion was examined as a means for pretreatment of sugarcane bagasse. Treatment conditions were optimized so that following enzymatic hydrolysis, pretreated bagasse would give 65.1 g sugars/100 g starting bagasse. Released sugars comprised 38.9 g glucose, 0.6 g cellobiose, 22.1 g xylose, and 3.5 g arabinose, and were equivalent to 83% of the anhydroglucan and 84% of the anhydroxylan content of untreated bagasse. Optimum conditions were treatment for 30 S with saturated steam at 220 degrees C with a water-to-solids ratio of 2 and the addition of 1 g H(2)SO(4)/100 g dry bagasse. Bagasse treated in this manner was not inhibitory to fermentation by Saccharomyces uvarum except at low inoculum levels when fermentation time was extended by up to 24 h. Pretreated saccharified bagasse was inhibitory to Pachysolen tannophilus and this was attributed to the formation of acetate from the hydrolysis of acetyl groups present in hemicellulose. The major advantage of the pretreatment is the achievement of high total sugar yield with moderate enzyme requirement and only minor losses due to sugar decomposition.     

Citric acid production by solid state fermentation using sugarcane bagasse

A solid state fermentation (SSF) method was used to produce citric acid by Aspergillus niger DS 1 using sugarcane bagasse as a carrier and sucrose or molasses based medium as a moistening agent. Initially bagasse and wheat bran were compared as carrier. Bagasse was the most suitable carrier, as it did not show agglomeration after moistening with medium, resulting in better heat and mass transfer during fermentation and higher product yield. Different parameters such as moisture content, particle size, sugar level and methanol concentration of the medium were optimised and 75% moisture level, 31.8 g sugar/100 g dry solid, 4% (v/w) methanol and particles of the size between 1.2 and 1.6 mm were found to be optimal. Sucrose and clarified and non-clarified molasses medium were also tested as moistening agents for SSF and under optimised conditions, 20.2, 19.8 and 17.9 g citric acid /100 g of dry solid with yield of 69.6, 64.5 and 62.4% (based on sugar consumed) was obtained in sucrose, clarified and non-clarified molasses medium respectively, after 9 days of fermentation.