Sugarcane Bagasse Hemicellulosic Hydrolysate Research Articles

Simultaneous production of xylitol and arabitol by Candida tropicalis fermentation improving agro-industrial wastes valorization

Xylitol and arabitol are sugar alcohols with similar properties and applications. Although the biotechnological production of xylitol is already being explored, its coproduction with arabitol is still in the early stages. This study aimed to improve the coproduction of xylitol and arabitol by Candida tropicalis from sugarcane bagasse hemicellulosic hydrolysate. The most promising results were achieved with 2.2 g L−1 nitrogen, obtained by mixing 80% yeast hydrolysate and 20% corn steep water. For fermentations conducted in a bioreactor, the concentrations of xylitol (52.1 g L−1) and arabitol (4.2 g L−1) were 65 and 3.7 times higher, respectively, than those reported in the literature for similar processes, with productivities and yields of 0.24 g L−1 h−1 and 0.74 g g−1 for xylitol and 0.02 g L−1 h−1 and 0.43 g g−1 for arabitol. These results show promise for the coproduction of sugar alcohols from sugarcane bagasse hemicellulosic hydrolysate by C tropicalis.

Mapping potential solvents for inhibitors removal from sugarcane bagasse hemicellulosic hydrolysate and its impact on fermentability

Mapping potential solvents for inhibitors removal from sugarcane bagasse hemicellulosic hydrolysate and its impact on fermentability

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.

Production, Physicochemical and Structural Characterization of a Bioemulsifier Produced in a Culture Medium Composed of Sugarcane Bagasse Hemicellulosic Hydrolysate and Soybean Oil in the Context of Biorefineries

Biosurfactants are amphipathic molecules, biodegradable, with reduced toxicity. They can be synthesized by fermentative processes from oleaginous compounds and agro-industrial by-products. In this context, the present study describes the production and the physical, chemical, and structural characterization of the bioemulsifier secreted by the yeast Scheffersomyces shehatae 16-BR6-2AI in a medium containing hemicellulosic sugarcane bagasse hydrolysate combined with soybean oil. The bioemulsifier was produced in Erlenmeyer flasks and isolated; then, the physicochemical and structural characterization of the formed molecule was carried out. The following fermentation parameters were obtained: YX/S = 0.45, YP/S = 0.083, and productivity of 0.076 g/L/h. The bioemulsifier was found to be a polymer containing 53% of carbohydrates, 40.92% of proteins, and 6.08% of lipids, respectively. The FTIR spectrum confirmed the presence of functional groups such as amides, amines, and carbonyls. The bioemulsifier was stable over a range of temperature (−20 °C to 120 °C), salinity (1–15%), and pH (2–12). It was observed that the biomolecule has a better emulsifying action in organic solvents with a non-polar character. Therefore, this biomolecule is a potential substitute for synthetic surfactants and can be used in different applications.

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.

Short-term Adaptation Strategy Improved Xylitol Production by Candida guilliermondii on Sugarcane Bagasse Hemicellulosic Hydrolysate

In this work, we proposed a short-term adaptation strategy to improve xylitol production on sugarcane bagasse hemicellulosic hydrolysate through the maximization of Candida guilliermondii FTI 20037 tolerance to inhibitors. Hemicellulosic hydrolysate obtained by diluted acid hydrolysis (1.0% (wv−1) H2SO4, 1:10 solid/liquid ratio, 121 °C, 10 min) was concentrated up to fivefold to obtain hydrolysates with different concentration factors. Yeast was cultivated in each hydrolysate for 24-h and consecutively transferred to the subsequent more concentrated hydrolysate to obtain different adaptation degrees. Adapted cells were used as inoculum in fermentations with the same hydrolysate in which they were adapted. The performance of adapted and non-adapted yeast was compared to validate the adaptation strategy employed. The beneficial effects of adaptation were more pronounced in the hydrolysates with higher inhibitor concentration (twofold concentrated and non-treated, H2N; and fivefold concentrated and treated, H5). It improved xylose assimilation and xylitol production as well as xylitol yield and xylitol volumetric productivity in both hydrolysates. A 62.5% increase in productivity (0.24 to 0.39 gL−1 h−1) and a 15.7% increase in yield (0.51 to 0.59 gg−1) were observed for H5 hydrolysate, while for H2N hydrolysate these increases were 54.5 and 29.6%, respectively. Yeast adaptation also improved arabinose consumption and reduced glycerol production. The reduction in glycerol production indicates a greater tolerance of adapted cells to the inhibitors present in hydrolysates. Short-term adaptation proved to be an efficient strategy to improve yeast tolerance as well as its fermentative performance on sugarcane bagasse hemicellulosic hydrolysate.

Co-fermentation of sugarcane bagasse hydrolysate and molasses by Clostridium saccharoperbutylacetonicum: Effect on sugar consumption and butanol production

Co-fermentation of mixed sugars to produce butanol is an attractive route in sucrochemical production chains. Herein, high-level mixed sugars from sugarcane bagasse hemicellulosic hydrolysate (HH) and molasses (SCM) were investigated as potential substrates for acetone-butanol-ethanol (ABE) production in batch fermentation by Clostridium saccharoperbutylacetonicum DSM 14923. HH produced after hydrothermal pretreatment was concentrated 5-fold and was called concentrated hemicellulosic hydrolysate (CHH). The fermentation media that were investigated consisted solely of CHH and SCM and three CHH-to-SCM ratios were used to provide 30 g/L initial sugar concentrations and furan derivatives lower than 0.1 g/L. For CHH50/SCM50 and CHH75/SCM25, diluting CHH to concentrations of 15 g/L sugars and 22.5 g/L sugars, respectively, which were supplemented with SCM and nutrients, suffered growth inhibition as a function of the concentration of undissociated acid in the medium. The best-performing medium, CHH25/SCM75 (7.5 g/L and 22.5 g/L sugars from CHH and SCM, respectively and about 0.017 g/L furan derivatives), showed 97 % sugar consumption, and in the pH range of 5.5–6.5, undissociated acetic acid was not an inhibitory molecular form to C. saccharoperbutylacetonicum. After 30 h of fermentation, 7.8 and 9.8 g/L butanol and ABE were produced, respectively, which yielded 0.28 and 0.36 g/g. Based on our findings, C. saccharoperbutylacetonicum exhibits its potential and effective application for renewable butanol production by co-fermenting mixed sugars.

Enhanced Tolerance of Spathaspora passalidarum to Sugarcane Bagasse Hydrolysate for Ethanol Production from Xylose.

During the pretreatment and hydrolysis of lignocellulosic biomass to obtain a hydrolysate rich in fermentable sugars, furaldehydes (furfural and hydroxymethylfurfural), phenolic compounds, and organic acids are formed and released. These compounds inhibit yeast metabolism, reducing fermentation yields and productivity. This study initially confirmed the ability of Spathaspora passalidarum to ferment xylose and demonstrated its sensibility to the inhibitors present in the hemicellulosic sugarcane bagasse hydrolysate. Then, an adaptive laboratory evolution, with progressive increments of hydrolysate concentration, was employed to select a strain more resistant to hydrolysate inhibitors. Afterward, a central composite design was performed to maximize ethanol production using hydrolysate as substrate. At optimized conditions (initial cell concentration of 30 g/L), S. passalidarum was able to produce 19.4 g/L of ethanol with productivity, yield, and xylose consumption rate of 0.8 g/L.h and 0.4 g/g, respectively, in a sugarcane bagasse hemicellulosic hydrolysate. A kinetic model was developed to describe the inhibition of fermentation by substrate and product. The values obtained for substrate saturation and inhibition constant were Ks = 120.4 g/L and Ki = 1293.4 g/L. Ethanol concentration that stops cell growth was 30.1 g/L. There was an agreement between simulated and experimental results, with a residual standard deviation lower than 6%.

Novel potential yeast strains for the biotechnological production of xylitol from sugarcane bagasse

AbstractThis study aimed to screen the xylitol‐producing strains of Cyberlindnera xylosilytica and Wickerhamomyces rabaulensis for the bioconversion of the hemicellulosic fraction of sugarcane bagasse. Among the 16 strains tested, two of each species (C. xylosilytica UFMG‐CM‐Y309 and UFMG‐CM‐Y409, and W. rabaulensis UFMG‐CM‐Y3716 and UFMG‐CM‐Y3747) were selected on the basis of xylitol yield (Yp/s) and xylitol volumetric productivity (Qp) in YPX broth (yeast extract, 10 g L−1; peptone, 20 g L−1; and d‐xylose, 60 g L−1). These strains were cultivated in sugarcane bagasse hemicellulosic hydrolysate (SCHH) supplemented with ammonium sulfate, rice bran extract, and yeast extract. The xylitol yield was the highest in the strain C. xylosilytica UFMG‐CM‐Y‐309 with a production of 14.06 g L−1; xylitol yield, 0.63 g g−1; xylitol volumetric productivity, 0.20 g L−1 h−1. Xylitol yields ranged from 14% to 74% above those of other xylitol‐production yeast species. This work demonstrates the potential of biotechnological application of these yeasts for xylitol production. © 2021 Society of Chemical Industry and John Wiley & Sons, Ltd

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.

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.

Characterization of the solid residue generated in the detoxification step of sugarcane bagasse hemicellulosic hydrolysate and behavior in agricultural soils

ABSTRACT Overliming is an effective way of neutralizing and reducing the toxicity of the hydrolysates generated from acidic pretreatment of lignocellulosic biomass for ethanol production and others biotechnological products. Overliming generates a solid residue whose inadequate disposal may represent an environmental problem. This work aimed at the chemical characterization of the solid residue generated during the detoxification of the sugarcane bagasse hemicellulosic hydrolysate and evaluation of its behavior in soil. The solid residue was submitted to physicochemical and granulometric analysis and determination of the contents of sugars, metals and toxic compounds (acetic acid, furfural, hydroxymethylfurfural and phenols). The potential of the residue as corrective of soil acidity was determined by analyzing the quality attributes of soil correctives (neutralizing power – NP, relative total neutralizing power – RTNP, Ca and Mg contents and granulometry). The residue was also evaluated for its influence on soil microbial communities and toxicity through bioassays with Lactuca sativa seeds. The residue contributed to the overall improvement of soil chemical attributes. The levels of Ca, Mg, C, OM and CEC were increased, nutrients such as Zn, Fe, Ni, Cr and Mn were detected, and microbial communities were stimulated. Besides, the residue showed no significant values of toxic compounds and no toxicity to L. sativa seeds. The residue was able to reduce the soil pH and to keep it stable throughout the study period. As a higher amount of the residue was necessary to reach pH 7 than limestone, it should be used as an auxiliary corrective of acidity.

Increased acetic acid removal from sugarcane bagasse hemicellulosic hydrolysate by the yeast Issatchenckia occidentalis Y1’a in absence of glucose

Increased acetic acid removal from sugarcane bagasse hemicellulosic hydrolysate by the yeast Issatchenckia occidentalis Y1’a in absence of glucose

Towards enhanced n-butanol production from sugarcane bagasse hemicellulosic hydrolysate: Strain screening, and the effects of sugar concentration and butanol tolerance

Robust strains are essential towards success of n-butanol production from lignocellulosic feedstock. To find a suitable strain to convert a non-detoxified hemicellulosic hydrolysate of sugarcane bagasse, we first assessed the performance of four wild-type butanol-producing Clostridium strains (C. acetobutylicum DSM 6228, C. beijerinckii DSM 6422, C. saccharobutylicum DSM 13864, and C. saccharoperbutylacetonicum DSM 14923) in batch fermentations containing either xylose or glucose at 30 g L−1 as sole carbon sources. C. saccharoperbutylacetonicum was selected after achieving butanol yields as high as 0.31 g g−1 on glucose and 0.25 g g−1 on xylose. In a 48-h fermentation containing a mixture of sugars (93% xylose and 7% glucose) that mimicked the hydrolysate, C. saccharoperbutylacetonicum delivered the highest butanol concentration (14.5 g L−1) when the initial sugar concentration was 50 g L−1. Moreover, the selected strain achieved the highest butanol yield (0.29 g g−1) on xylose-rich media reported so far. Meanwhile, C. saccharoperbutylacetonicum produced 5.8 g butanol L−1 (0.22 g g−1 butanol yield) when fermenting a non-detoxified sugarcane bagasse hemicellulosic hydrolysate enriched with xylose (30 g total sugars L−1). Although sugars were not exhausted (4.7 g residual sugars L−1) even after 72 h because of the presence of lignocellulose-derived microbial inhibitors, these results show that C. saccharoperbutylacetonicum is a robust wild-type strain. This microorganism with high butanol tolerance and yield on xylose can, therefore, serve as the basis for the development of improved biocatalysts for production of butanol from non-detoxified sugarcane bagasse hemicellulosic hydrolysate.

Co-culture strategy for improved 2G bioethanol production using a mixture of sugarcane molasses and bagasse hydrolysate as substrate

Mixed sugar co-fermentation represents an interesting fermentation strategy to improve bioethanol production from low-cost raw materials, such as sugarcane bagasse. The aim of this study was to evaluate a mixture of sugars (hexoses and pentoses) from sugarcane bagasse hemicellulosic hydrolysate diluted with sugarcane molasses as substrate to be converted either in monoculture or co-culture fermentations. A co-culture fermentation technique using hexoses-fermenting yeasts (Saccharomyces cerevisiae: from Santa Adélia Mill, an industrial strain (SA) and a respiratory-deficient mutant strain (ScP)) together with xylose-fermenting yeasts (Scheffersomyces stipitis (SS) and Spathaspora passalidarum (SP)) was carried out to enhance bioethanol production. Co-culture fermentation in a medium with a high mixed sugar concentration (100 g.L−1) resulted in a complete sugar consumption, ethanol titer of 30.2 g.L−1 and increased ethanol productivity (Qp =4.44 g.L−1. h−1) using wild type strains (SP + SA). In contrast, the maximum ethanol titer (49.2 g.L−1) was reached during co-culture performed with S. stipitis and the respiratory-deficient mutant strain of S. cerevisiae, however ethanol productivity (Qp =0.60 g.L−1. h−1) decreased due to the poor fermentation performance of the mutant strain. This work suggests that improved efficiency and good scalability of the mixed sugar fermentation process makes an important basis for the economic viability of bioethanol production from lignocelluloses.

Bioethanol Production From Sugarcane Bagasse Hemicellulose Hydrolysate by Immobilized S. shehatae in a Fluidized Bed Fermenter Under Magnetic Field

Bioethanol production from sugarcane bagasse hemicellulosic hydrolysate using immobilized Scheffersomyces shehatae on magnetic biosupports in a fluidized bed bioreactor assisted by magnetic field has been studied. Fermentations were carried out in two experimental setups operating in a magnetically stabilized bed mode with transversal and axial magnetic field lines at 8 and 12 kA/m, respectively. The best results were attained when experiments were carried out using a fermenter assisted by axial field whose ethanol/substrate yield and ethanol productivity were 0.15 ± 0.8E-3 g/g and 0.055 ± 0.3E-3 g/gh. These values were 12 and 34%, respectively, higher than those observed in fermentations with transversal field lines (Tukey’s test, p < 0.05). Thus, these results are attractive and can be considered as a technological advance in the bioethanol production from biomass using this unconventional fermentation technology.

Repeated batches as a feasible industrial process for hemicellulosic ethanol production from sugarcane bagasse by using immobilized yeast cells

Currently, sugarcane bagasse (SB) is the most abundant agricultural residue generated in Brazil. Given that hemicelluloses can reach up to 30% of SB, bioconversion of this fraction into second generation ethanol (2G) is essential for the success of biorefinery based operations. For 2G ethanol production, techniques such as immobilization process could be an interesting strategy to improve process productivity and must receive special investigation. Cell immobilization of the native Brazilian pentose wild converting yeast, Scheffersomyces shehatae UFMG-HM 52.2, was proposed for the production of 2G ethanol from SB hemicellulosic hydrolysate. A 23 full experimental design was constructed with varying concentrations of sodium alginate (1.0, 1.5 and 2.0% w/v), and calcium chloride (0.1 M, 0.15 M and 0.2 M) and conditioning time (12, 18 and 24 h). Through statistical analysis, it was determined that highest ethanol yield (YP/S of 0.32 g/g) and productivity (QP of 0.146 g/L.h) were obtained with immobilization conditions of 1% sodium alginate, 0.2 M calcium chloride and 12 h of conditioning time. Repeated batches were conducted employing these defined conditions, showing the feasibility to use the system for 5 consecutive cycles. Results highlighted the use of proposed approach for ethanol production, promoting its inclusion in biorefinery operation portfolios. Hemicellulosic hydrolysate from sugarcane bagasse: a large available carbon source; S. shehatae UFMG-HM 52.2 is a Brazilian wild native pentose fermenting yeast; Immobilization conditions for this yeast were defined for ethanol production; Stability in ethanol production was demonstrated in 5 repeated consecutive batches; Our approach was demonstrated feasible for industrial 2G ethanol process development.