Sugarcane Bagasse Hemicellulose Research Articles

Strategy to reduce acetic acid in sugarcane bagasse hemicellulose hydrolysate concomitantly with xylitol production by the promising yeast Cyberlindnera xylosilytica in a bioreactor.

The yeast Cyberlindnera xylosilytica UFMG-CM-Y309 has been identified as a promising new xylitol producer from sugarcane bagasse hemicellulosic hydrolysate (SCHH). However, SCHH pretreatment process generates byproducts, which are toxic to cell metabolism, including furans, phenolic compounds, and carboxylic acids, such as acetic acid, typically released at high concentrations. This research aims to reduce acetic acid in sugarcane hemicellulose hydrolysate concomitantly with xylitol production by yeast strain Cy. xylosilytica UFMG-CM-Y309 in a bioreactor by strategically evaluating the influence of volumetric oxygen transfer coefficient (kLa) (21 and 35h-1). Experiments were conducted on a bench bioreactor (2L volumetric capacity) at different initial kLa values (21 and 35h-1). SCHH medium was supplemented with rice bran extract (10gL-1) and yeast extract (1gL-1). Cy. xylosilytica showed high xylitol production performance (19.56gL-1), xylitol yield (0.56gg-1) and, maximum xylitol-specific production rate (μpmáx 0.20 gxylitol·g-1h-1) at kLa value of 21h-1, concomitantly slowing the rate of acetic acid consumption. A faster acetic acid consumption (100%) by Cy. xylosilytica was observed at kLa of 35h-1, concomitantly with an increase in maximum cellular growth (14.60gL-1) and reduction in maximum xylitol production (14.56gL-1 and Yp/s 0.34gg-1). This study contributes to pioneering research regarding this yeast performance in bioreactors, emphasizing culture medium detoxification and xylitol production.

Microbial oil and biodiesel production in an integrated sugarcane biorefinery: Techno-economic and life cycle assessment

Biodiesel and bioethanol play an important role as renewable liquid fuels. Bagasse, a by-product from the bioethanol industry, can generate a “sugarcane bagasse hemicellulose hydrolysate” (SCBH) that contains fermentable sugars, mainly xylose. Oleaginous yeasts (eg., Rhodotorula toruloides) can grow in SCBH, producing microbial oil (MO), a source of triacylglycerol for biodiesel production. The integration of bioethanol and biodiesel (from MO) production may be a promising approach in order to exploit synergies between bioethanol and biodiesel processes within a biorefinery. This integration may improve the economic and environmental performance of both processes. This work presents the techno-economic-environmental analysis of the integrated production of first-generation bioethanol, bioelectricity, and biodiesel in a Brazilian sugarcane biorefinery, where MO from the yeast R. toruloides feeds the biodiesel unit. The biorefinery, processing 4.0 million t of sugarcane per harvest, produces 71.7 m3/h of bioethanol, 2.55 m3/h of biodiesel (that can replace 75.6% of the diesel demand in the field), and 86.3 MW of surplus bioelectricity. A life cycle assessment shows that the integrated biorefinery had a lower environmental impact than the first-generation bioethanol plant. The integrated process exhibits a positive economic performance (net present value of approx. 110 million of dollars and internal rate of return of about 14.5% per year, higher than the minimum acceptable rate of return, assumed as 11% per year), indicating that this is a feasible industrial option. Sensitivity analysis shows that R&D should mainly focus on the MO bioreactor operation.

Cell Immobilization Using Alginate-Based Beads as a Protective Technique against Stressful Conditions of Hydrolysates for 2G Ethanol Production.

The development of biorefineries brings the necessity of an efficient consumption of all sugars released from biomasses, including xylose. In addition, the presence of inhibitors in biomass hydrolysates is one of the main challenges in bioprocess feasibility. In this study, the application of Ca-alginate hybrid gels in the immobilization of xylose-consuming recombinant yeast was explored with the aim of improving the tolerance of inhibitors. The recombinant yeast Saccharomyces cerevisiae GSE16-T18SI.1 (T18) was immobilized in Ca-alginate and Ca-alginate–chitosan hybrid beads, and its performance on xylose fermentation was evaluated in terms of tolerance to different acetic acid concentrations (0–12 g/L) and repeated batches of crude sugarcane bagasse hemicellulose hydrolysate. The use of the hybrid gel improved yeast performance in the presence of 12 g/L of acetic acid, achieving 1.13 g/L/h of productivity and reaching 75% of the theoretical ethanol yield, with an improvement of 32% in the xylose consumption rate (1:1 Vbeads/Vmedium, 35 °C, 150 rpm and pH 5.2). The use of hybrid alginate–chitosan gel also led to better yeast performance at crude hydrolysate, yielding one more batch than the pure-alginate beads. These results demonstrate the potential of a hybrid gel as an approach that could increase 2G ethanol productivity and allow cell recycling for a longer period.

Hydrogen production by Enterobacter sp. LBTM 2 using sugarcane bagasse hemicellulose hydrolysate and a synthetic substrate: understanding and controlling toxicity

Abstract Sugars released by thermochemical pretreatment of lignocellulosic biomass are possible substrate for hydrogen production. However, the major drawback for bacterial fermentation is the toxicity of weak acids and furan derivatives normally present in such substrate. This study aimed to investigate the metabolism involved in hydrogen production by the isolate Enterobacter LBTM2 using 10, 20 and 30-fold diluted synthetic (SH) and sugarcane bagasse hemicellulose (SBH) hydrolysates. In addition, the effects of acetic acid, formic acid and furfural on the bacterial metabolism, as well as detoxification of SBH with activated carbon and molecularly imprinted polymers on the hydrogen production were assessed. The results showed the best hydrogen yield was 0.46 mmol H2/mmol sugar for 20-times diluted SH, which was 2.3-times higher than obtained in SBH experiments. Bacterial growth and hydrogen production were negatively affected by 0.8 g/L of acetic acid when added alone, but were totally inhibited when formic acid (0.4 g/L) and furfural (0.3 g/L) were also supplied. However the maximum hydrogen production of SBH20 has duplicated when 3% of powdered activated carbon was added to the SBH experiment. The results presented herein can be helpful in understanding the bottlenecks in biohydrogen production and could contribute towards development of lignocellulosic biorefinery.

Three-stage repeated-batch immobilized cell fermentation to produce butanol from non-detoxified sugarcane bagasse hemicellulose hydrolysates

To enable the production of butanol with undiluted, non-detoxified sugarcane bagasse hemicellulose hydrolysates, this study developed a three-staged repeated-batch immobilized cell fermentation in which the efficiency of a 3D-printed nylon carrier to passively immobilize Clostridium saccharoperbutylacetonicum DSM 14923 was compared with sugarcane bagasse. The first stage consisted of sugarcane molasses fermentation, and in the second stage, non-detoxified sugarcane bagasse hemicellulose hydrolysates (SBHH) was pulse-fed to sugarcane molasses fermentation. In the next four batches, immobilized cells were fed with undiluted SBHH supplemented with molasses, and SBHH-derived xylose accounted for approximately 50% of the sugars. Bagasse was a superior carrier, and the average xylose utilization (33%) was significantly higher than the treatment with the 3D-printed carrier (16%). Notably, bagasse allowed for 43% of the butanol to be SBHH-derived. Overall, cell immobilization on lignocellulosic materials can be an efficient strategy to produce butanol from repeated-batch fermentation of non-detoxified hemicellulose hydrolysates.

From by- to bioproducts: selection of a nanofiltration membrane for biotechnological xylitol purification and process optimization

Xylitol, an alcohol sugar with diverse applications, is commonly synthesized by chemical routes on an industrial scale. This polyalcohol can also be obtained by fermentation of lignocellulosic biomass. However, downstream purification is still a bottleneck that increases the costs and limits the yield of bioxylitol production. This study aimed to develop a novel approach for purification of xylitol obtained by fermentation of sugarcane bagasse hemicellulose hydrolysate. After nanofiltration membrane selection, process conditions were optimized by surface response methodology. Four nanofiltration membranes were tested: NF (polypiperazine amide), NF90 (fully aromatic polyamide), and NP010 and NP030 (polyethersulfones). NF had the lowest fouling tendency and provided the highest xylitol–protein separation factor and feed–permeate color difference. Factorial design studies revealed that permeate flux and color parameter a* were significantly influenced by pH and pressure. Xylitol productivity and lightness difference were affected by temperature. The best nanofiltration conditions were 40 bar, 40 °C, and pH 5.4. Fermented hydrolysate was subjected to microfiltration and ultrafiltration prior to nanofiltration to minimize fouling. Results were satisfactory, with a xylitol purification factor of 3.3, protein separation factor of 8.4, and color removal of 96.0%. Nanofiltration can be used as a preceding step to crystallization in the purification of xylitol obtained from sugarcane bagasse hydrolysate.

Enabling butanol production from crude sugarcane bagasse hemicellulose hydrolysate by batch-feeding it into molasses fermentation

Butanol is a chemical and advanced biofuel whose fermentative production from hemicellulose hydrolysates is hindered by lignocellulose-derived microbial inhibitory compounds. In this work, Clostridium saccharoperbutylacetonicum DSM 14923 was not able to ferment a sugarcane hemicellulose hydrolysate supplemented with either laboratory-grade nutrients or sugarcane molasses. To circumvent this problem, the crude hemicellulose hydrolysate was fed, after 24 h, to a molasses fermentation containing 45 g/L total reducing sugars. Without the need of supplementing nutrients, the culture was able to co-ferment sucrose, glucose, fructose, and xylose (conversion of sucrose and xylose were 81 and 90 %, respectively) in a fermentation containing a diluted molasses-to-hydrolysate volume ratio of 3:1. Butanol yield (0.31 g/g) was remarkable, and butanol titer was 10.0 g/L after 72 h of fermentation. Therefore, this research demonstrated that sugarcane molasses ‒ a by-product of the sugar industry rich in sucrose and nutrients ‒ can be an efficient feedstock for enabling the production of butanol from sugarcane bagasse hemicellulose hydrolysate.

Repeated batches as a strategy for high 2G ethanol production from undetoxified hemicellulose hydrolysate using immobilized cells of recombinant Saccharomyces cerevisiae in a fixed-bed reactor

BackgroundThe search for sustainable energy sources has become a worldwide issue, making the development of efficient biofuel production processes a priority. Immobilization of second-generation (2G) xylose-fermenting Saccharomyces cerevisiae strains is a promising approach to achieve economic viability of 2G bioethanol production from undetoxified hydrolysates through operation at high cell load and mitigation of inhibitor toxicity. In addition, the use of a fixed-bed reactor can contribute to establish an efficient process because of its distinct advantages, such as high conversion rate per weight of biocatalyst and reuse of biocatalyst.ResultsThis work assessed the influence of alginate entrapment on the tolerance of recombinant S. cerevisiae to acetic acid. Encapsulated GSE16-T18SI.1 (T18) yeast showed an outstanding performance in repeated batch fermentations with cell recycling in YPX medium supplemented with 8 g/L acetic acid (pH 5.2), achieving 10 cycles without significant loss of productivity. In the fixed-bed bioreactor, a high xylose fermentation rate with ethanol yield and productivity values of 0.38 gethanol/gsugars and 5.7 g/L/h, respectively were achieved in fermentations using undetoxified sugarcane bagasse hemicellulose hydrolysate, with and without medium recirculation.ConclusionsThe performance of recombinant strains developed for 2G ethanol production can be boosted strongly by cell immobilization in alginate gels. Yeast encapsulation allows conducting fermentations in repeated batch mode in fixed-bed bioreactors with high xylose assimilation rate and high ethanol productivity using undetoxified hemicellulose hydrolysate.

Flow synthesis, characterization, anticoagulant activity of xylan sulfate from sugarcane bagasse

High-value utilization of hemicellulose is critical to improve the append value of integrated biorefineries. In this research, the alkali-soluble sugarcane bagasse hemicellulose was sulfated using chlorosulfonic acid and N,N-dimethylformamide/LiCl under homogeneous conditions. With the aid of flow technique, a rapid, mild, and efficient method for the synthesis of xylan sulfate with high molecular weight and controllable degree of substitution was achieved. The results showed that the reaction time and the degradation of xylan chain were drastically reduced compared to the “in flask” batch conditions. High molecular weight of the product (Mw = 148,217) with a reasonable degree of substitution (DS = 1.49) could be obtained even at room temperature in 10 min under the present flow system. Anticoagulant experiments showed good anticoagulant activity of the resultant xylan sulfate, which could significantly prolong the activated partial thromboplastin time and thrombin time. This work not only provides a novel method for the synthesis of xylan sulfate, but also offers new opportunities for the production of other functional polysaccharide derivatives under the flow reaction conditions.

Enhanced ethanol production from sugarcane bagasse hydrolysate with high content of inhibitors by an adapted barnettozyma californica

Bioethanol production from acid hydrolysate of sugarcane bagasse's hemicellulose was studied using an adapted new yeast strain, Barnettozyma californica HNMA‐5. The growth rate and ethanol production were studied by using the adapted and the parental strains in Sugarcane Bagasse Hydrolysate (SBH) and Concentrated Sugarcane Bagasse Hydrolysate (CSBH). The hydrolysate concentration resulted in an increase of total sugar from 34 to 51.8 g L−1 and an approximately twofold increase in nonvolatile toxic compounds like phenol (1.017–2.11 g L−1) in CSBH. An adaptation of the yeast strain to CSBH resulted in improved growth ability and ethanol production, whereas no significant effect was observed in SBH. The adapted yeast showed a promising ethanol production of 4.804 g L−1 after 24 h compared to the parental strain, which produced 1.233 g L−1 after 72 h of fermentation. The adapted yeast could produce about four times more ethanol than the parental strain. In addition, the lag phase decreased from 9 to 5 h and productivity increased 10‐fold. Furthermore, the hydrolysate concentration and the yeast's adaptation were effective methods to improve ethanol production in CSBH. Our data indicate that the new yeast isolate, B. californica HNMA‐5 could be successfully applied to lignocellulosic ethanol production. © 2017 American Institute of Chemical Engineers Environ Prog, 37: 1169–1175, 2018

Hemicellulose and lignin removal to improve the enzymatic digestibility and ethanol production

Fourteen herbaceous energy crops were selected to investigate their recalcitrance to cellulosic enzyme. The results about enzymatic hydrolysis of sorghum and Pennisetum hybrids indicated that both hemicellulose and lignin content had a negative influence on enzymatic digestibility (ED), especially for the latter.Furthermore, liquid hot water (LHW) and aqueous ammonia (AA) methods were applied to enhance the ED of sugarcane bagasse (SCB). A high ED of 90% was obtained for sample with 50% removal of xylan and lignin in the AA process, which was 20% higher than that of LHW due to the significant removal of lignin hindering and exposing of fibers. However, the total sugars recovery of LHW were about 10% higher than that of AA resulted to the high yield of hemicellulose-derived sugars.Moreover, SCB hemicellulose and lignin were removed with the help of LHW and following AA process. The ethanol concentration reached to 30.6 g/L after a fed-batch enzymatic hydrolysis following simultaneous saccharification and fermentation process with a high substrates loadings of 20% (w/v), low enzyme loading of 20 FPU/g glucan, and low fermentation time of 24 h.

Evaluation of hydrogen and methane production from sugarcane bagasse hemicellulose hydrolysates by two-stage anaerobic digestion process

This study aimed at optimizing the net energy recovery from hydrogen and methane production through anaerobic digestion of the hemicellulose hydrolysate (HH) obtained by desirable conditions (DC) of autohydrolysis pretreatment (AH) of sugarcane bagasse (SB). Anaerobic digestion was carried out in a two-stage (acidogenic-methanogenic) batch system where the acidogenic phase worked as a hydrolysis and biodetoxification step. This allowed the utilization of more severe AH pretreatment conditions, i.e. T=178.6°C and t=55min (DC3) and T=182.9°C and t=40.71min (DC4). Such severe conditions resulted in higher extraction of hemicelluloses from SB (DC1=68.07%, DC2=48.99%, DC3=77.40% and DC4=73.90%), which consequently improved the net energy balance of the proposed process. The estimated energy from the combustion of both biogases (H2 and CH4) accumulated during the two-stage anaerobic digestion of HH generated by DC4 condition was capable of producing a net energy of 3.15MJ·kgSB−1dry weight.

Optimization of biohydrogen production from sugarcane bagasse by mixed cultures using a statistical method

Abstract The aim of this study is to determine the optimum condition for biohydrogen production from sugarcane bagasse (SCB) hydrolysate using a central composite design and response surface methodology (RSM). SCB was hydrolyzed with 0.5% (v/v) sulfuric acid at 121 °C, 0.15 MPa for 60 min in an autoclave at a solid to liquid ratio of 1:15 (g:mL). Heat-treated bacterium obtained from a hydrogen producing fermentor was used as the inoculum. The interaction of three factors, i.e., substrate concentration, substrate:buffer ratio and inoculum:substrate ratio on hydrogen production potential (P) were investigated. The results indicated that the substrate concentration, substrate:buffer ratio and inoculum:substrate ratio had a significant influence effect on P. An optimal condition was found at substrate concentration of 22.77 g-total sugar L−1, 4.31 substrate:buffer ratio, and 0.31 inoculum:substrate ratio resulted in a maximum P of 6980 mL H2 L−1. The confirmation experiment results indicated that optimum P was statistically significant, from the predicted value obtained by RSM which suggests that RSM could be efficiently used to optimize a biohydrogen production from SCB hydrolysate using mixed cultures. These results indicates that the SCB hemicellulose hydrolysate is suitable as a fermentation media for producing biohydrogen. This approach will add value to SCB by converting agricultural waste into a safe and clean form of energy.

Screening of Yeasts for Selection of Potential Strains and Their Utilization for In Situ Microbial Detoxification (ISMD) of Sugarcane Bagasse Hemicellulosic Hydrolysate

Many toxic compounds are produced and released in the hemicellulosic hydrolyzates during the acid pretreatment step, which are required for the disruption of the lignocelluloses matrix and sugars release. The conventional methods of detoxification i.e. overliming, activated charcoal, ion exchange or even membrane-based separations have the limitations in removal of these toxic inhibitors in fermentation process. Hence, it is imperative to explore biological methods to overcome the inhibitors by minimizing the filtration steps, sugar loss and chemical additions. In the present study we screened sixty-four strains of yeasts to select potential strains for detoxification of furfural, acetic acid, ferulic acid, 5-hydroxymethyl furfural (5-HMF) as carbon and energy source. Among these strains Pichia occidentalis M1, Y1'a, Y1'b and Y3' showed a significant decrease in the toxic compounds but we selected two best yeast strains i.e. P. occidentalis Y1'a and P. occidentalis M1 for the further experiments with an aim to remove the fermentation inhibitors. The yeasts P. occidentalis Y1'a and P. occidentalis M1 were grown aerobically in sugarcane bagasse hemicellulose hydrolysate under submerged cultivation. For each yeast, a 2(2) full factorial design was performed considering the variables-pH (4.0 or 5.0) and agitation rate (100 or 300rpm), and the percentage removal of HMF, furfural, acetic acid and phenols from hemicellulosic hydrolysates were responsive variables. After 96h of biological treatment, P. occidentalis M1 and P. occidentalis Y1'a showed 42.89 and 46.04% cumulative removal of inhibitors, respectively.

Enhanced enzymatic hydrolysis of sugarcane bagasse hemicellulose using recombinant glucose oxidase expressed by Pichia pastoris

To demonstrate the role of glucose oxidase (GOD) on the enzyme-catalyzed production of xylose from SCB hemicellulose, a variant of the GOD gene, which contains two amino acid substitutions, was cloned from Aspergillus niger CICC40179. Three-dimension structure modeling showed that the two variable amino acid residues were positioned on the surface of the protein molecule. The GOD gene was expressed in Pichia pastoris. Approximately 16.31U/mL of GOD was obtained after 3 days of fermentation in the optimized medium. The catalytic characteristic of GOD was considered to apply in the production of xylose from hemicellulose. The pH value, temperature and the loading of GOD were optimized using the Box–Behnken design to improve the yield of xylose. The xylose yield was increased by 46% in 16h of hydrolysis by adding GOD when the reaction was conducted under the optimal conditions (pH 5.1, temperature 44.9°C and 31.68U GOD per gram substrate). Glucose was not detected in the hydrolysis system supplemented with GOD. This is the first study demonstrating the application of glucose oxidase (GOD) on the enzyme-catalyzed production of xylose from SCB hemicellulose. The newly developed enzymatic hydrolysis system can contribute to the industrial production of xylose.

Xylitol production by yeasts isolated from rotting wood in the Galápagos Islands, Ecuador, and description of Cyberlindnera galapagoensis f.a., sp. nov.

This study evaluated D-xylose-assimilating yeasts that are associated with rotting wood from the Galápagos Archipelago, Ecuador, for xylitol production from hemicellulose hydrolysates. A total of 140 yeast strains were isolated. Yeasts related to the clades Yamadazyma, Kazachstania, Kurtzmaniella, Lodderomyces, Metschnikowia and Saturnispora were predominant. In culture assays using sugarcane bagasse hemicellulose hydrolysate, Candida tropicalis CLQCA-24SC-125 showed the highest xylitol production, yield and productivity (27.1 g L(-1) xylitol, Y p/s (xyl) = 0.67 g g(-1), Qp = 0.38 g L(-1). A new species of Cyberlindnera, strain CLQCA-24SC-025, was responsible for the second highest xylitol production (24 g L(-1), Y p/s (xyl) = 0.64 g g(-1), Qp = 0.33 g L(-1) h(-1)) on sugarcane hydrolysate. The new xylitol-producing species Cyberlindnera galapagoensis f.a., sp. nov., is proposed to accommodate the strain CLQCA-24SC-025(T) (=UFMG-CM-Y517(T); CBS 13997(T)). The MycoBank number is MB 812171.

Evaluation of novel xylose-fermenting yeast strains from Brazilian forests for hemicellulosic ethanol production from sugarcane bagasse.

Bioconversion of hemicellulosic hydrolysates into ethanol with the desired yields plays a pivotal role for the overall success of biorefineries. This paper aims to evaluate the ethanol production potential of four native strains of Scheffersomyces shehatae (syn. Candida shehatae) viz. S. shehatae BR6-2AI, CG8-8BY, PT1-1BASP and BR6-2AY, isolated from Brazilian forests. These strains were grown in commercial d-xylose-supplemented synthetic medium and sugarcane bagasse hemicellulose hydrolysate. S. shehatae BR6-2AY showed maximum ethanol production [0.48 ± 0.019 g g−1, 95 ± 3.78 % fermentation efficiency (FE)] followed by S. shehatae CG8-8BY (0.47 ± 0.016 g g−1, 93 ± 3.12 % FE), S. shehatae BR6-2AI (0.45 ± 0.01 g g−1, 89 ± 1.71 % FE) and S. shehatae PT1-1BASP (0.44 ± 0.02 g g−1, 86 ± 3.37 % FE) when grown in synthetic medium. During the fermentation of hemicellulose hydrolysates, S. shehatae CG8-8BY and S. shehatae BR6-2AY showed ethanol production (0.30 ± 0.05 g g−1, 58 ± 0.02 % FE) and (0.21 ± 0.01 g g−1, 40 ± 1.93 % FE), respectively.

Ultrasonic pretreatment and acid hydrolysis of sugarcane bagasse for succinic acid production using Actinobacillus succinogenes

Immense interest has been devoted to the production of bulk chemicals from lignocellulose biomass. Diluted sulfuric acid treatment is currently one of the main pretreatment methods. However, the low total sugar concentration obtained via such pretreatment limits industrial fermentation systems that use lignocellulosic hydrolysate. Sugarcane bagasse hemicellulose hydrolysate is used as the carbon and nitrogen sources to achieve a green and economical production of succinic acid in this study. Sugarcane bagasse was ultrasonically pretreated for 40 min, with 43.9 g/L total sugar obtained after dilute acid hydrolysis. The total sugar concentration increased by 29.5 %. In a 3-L fermentor, using 30 g/L non-detoxified total sugar as the carbon source, succinic acid production increased to 23.7 g/L with a succinic acid yield of 79.0 % and a productivity of 0.99 g/L/h, and 60 % yeast extract in the medium could be reduced. Compared with the detoxified sugar preparation method, succinic acid production and yield were improved by 20.9 and 20.2 %, respectively.

Carboxyl Modification of Sugarcane Bagasse Hemicelluloses With Succinic Anhydride in Aqueous Solution

Abstract In this paper, we describe the modification of sugarcane bagasse with succinic anhydride to introduce carboxylic functions to sugarcane bagasse. The properties of the sugarcane bagasse hemicelluloses change after carboxyl modification. The influences of the chemical reaction on the conditions, the chemical composition, and the thermal stability of the modified product are described. One gram of dried sugarcane bagasse was modified using 3.0 g succinic anhydride and 0.1 g N-bromination succinic imide with a reaction time of 6 h at 70°C. The obtained materials were characterized via Fourier transform infrared spectroscopy, nuclear magnetic resonance, thermal analysis, and scanning electron microscopy.

Evaluation of ethanol production by a new isolate of yeast during fermentation in synthetic medium and sugarcane bagasse hemicellulosic hydrolysate

A new xylose fermenting yeast was isolated from over-ripe banana by enrichment in xylose-containing medium. The phylogenetic analysis of ITS1-5.8S-ITS2 region sequences of ribosomal RNA of isolate BY2 revealed that it shows affiliation to genus Pichia and clades with Pichia caribbica. In batch fermentation, Pichia strain BY2 fermented xylose, producing 15 g l−1 ethanol from 30 g l−1 xylose under shaking conditions at 28°C, with ethanol yield of 0.5 g g−1 and volumetric productivity of 0.31 g l−1 h−1. The optimum pH range for ethanol production from xylose by Pichia strain BY2 was 5–7. Pichia strain BY2 also produced 6.08 g l−1 ethanol from 30 g l−1 arabinose. Pichia strain BY2 can utilize sugarcane bagasse hemicellulose acid hydrolysate for alcohol production, efficiency of fermentation was improved by neutralization, and sequential use of activated charcoal adsorption method. Percent total sugar utilized and ethanol yield for the untreated hydrolysate was 17.14% w/v and 0.33 g g−1, respectively, compared with 66.79% w/v and 0.45 g g−1, respectively, for treated hemicellulose acid hydrolysate. This new yeast isolate showed ethanol yield of 0.45 g g−1 and volumetric productivity of 0.33 g l−1 h−1 from sugarcane bagasse hemicellulose hydrolysate detoxified by neutralization and activated charcoal treatment, and has potential application in practical process of ethanol production from lignocellulosic hydrolysate.