Ultra-structural mapping of sugarcane bagasse after oxalic acid fiber expansion (OAFEX) and ethanol production by Candida shehatae and Saccharomyces cerevisiae

Fabrication and Characterization of Effective Biochar Biosorbent Derived from Agricultural Waste to Remove Cationic Dyes from Wastewater

The main aim of this work is to treat sugarcane bagasse agricultural waste and prepare an efficient, promising, and eco-friendly adsorbent material. Biochar is an example of such a material, and it is an extremely versatile and eco-friendly biosorbent to treat wastewater. Crystal violet (CV)-dye and methylene blue (MB)-dye species are examples of serious organic pollutants. Herein, biochar was prepared firstly from sugarcane bagasse (SCB), and then a biochar biosorbent was synthesized through pyrolysis and surface activation with NaOH. SEM, TEM, FTIR, Raman, surface area, XRD, and EDX were used to characterize the investigated materials. The reuse of such waste materials is considered eco-friendly in nature. After that, the adsorption of MB and CV-species from synthetically prepared wastewater using treated biochar was investigated under various conditions. To demonstrate the study’s effectiveness, it was attempted to achieve optimum effectiveness at an optimum level by working with time, adsorbent dose, dye concentration, NaCl, pH, and temperature. The number of adsorbed dyes reduced as the dye concentrations increased and marginally decreased with NaCl but increased with the adsorbent dosage, pH, and temperature of the solution increased. Furthermore, it climbed for around 15 min before reaching equilibrium, indicating that all pores were almost full. Under the optimum condition, the removal perecentages of both MB and CV-dyes were ≥98%. The obtained equilibrium data was represented by Langmuir and Freundlich isotherm models. Additionally, the thermodynamic parameters were examined at various temperatures. The results illustrated that the Langmuir isotherm was utilized to explain the experimental adsorption processes with maximum adsorption capacities of MB and CV-dyes were 114.42 and 99.50 mgg⁻¹, respectively. The kinetic data were estimated by pseudo-first and pseudo-second-order equations. The best correlation coefficients of the investigated adsorption processes were described by the pseudo-second-order kinetic model. Finally, the data obtained were compared with some works published during the last four years.

Lignin-Cellulose Nanocrystals from Hemp Hurd as Light-Coloured Ultraviolet (UV) Functional Filler for Enhanced Performance of Polyvinyl Alcohol Nanocomposite Films

Lignin is a natural light-coloured ultraviolet (UV) absorber; however, conventional extraction processes usually darken its colour and could be detrimental to its UV-shielding ability. In this study, a sustainable way of fabricating lignin-cellulose nanocrystals (L-CNCs) from hemp hurd is proposed. A homogeneous morphology of the hemp particles was achieved by ball milling, and L-CNCs with high aspect ratio were obtained through mild acid hydrolysis on the ball-milled particles. The L-CNCs were used as filler in polyvinyl alcohol (PVA) film, which produced a light-coloured nanocomposite film with high UV-shielding ability and enhanced tensile properties: the absorption of UV at wavelength of 400 nm and transparency in the visible-light region at wavelength of 550 nm was 116 times and 70% higher than that of pure PVA, respectively. In addition to these advantages, the nanocomposite film showed a water vapour transmission property comparable with commercial food package film, indicating potential applications.

Comparative data on effects of alkaline pretreatments and enzymatic hydrolysis on bioemulsifier production from sugarcane straw by Cutaneotrichosporon mucoides

Bioemulsifiers are surface active compounds which could be potentially used in food processing, cosmetic sector and oil recovery. Sugarcane straw (SS), was used as the raw substrate for the production of bio-emulsifiers (BE) by Cutaneotrichosporon mucoides. Three different delignification strategies using dilute sodium hydroxide, sodium sulfite and ammonium hydroxide followed by enzymatic hydrolysis (Cellic CTec 2, 7.5% total solids, 15 FPU/g, 72 h) were studied. Enzyme hydrolysis of ammonium hydroxide pretreated SS showed a maximum of 62.19 ± 0.74 g/l total reducing sugars with 88.35% hydrolytic efficiency (HE) followed by sodium hydroxide (60.06 ± 0.33 g/l; 85.40% HE) and sodium sulfite pretreated SS (57.22 ± 0.52 g/l; 84.71% HE), respectively. The ultrastructure of SS (native and delignified) by fourier transform-infrared and near infrared spectroscopy, revealed notable structural differences. The fermentation of hydrolysates by C. mucoides into bioemulsifiers showing emulsification index (EI) of 54.33%, 48.66% and 32.66% from sodium sulfite, sodium hydroxide, and ammonium hydroxide pretreated SS, respectively.

Radiation-Induced Structural Changes of Miscanthus Biomass

Efficient pretreatment is a prerequisite for lignocellulosic biomass biorefinery due to the structure of lignocellulose. This study is a first-time investigation into the structural changes of Miscanthus biomass treated with 60Co γ-ray irradiation in different doses up to 1200 kGy. The structural properties of the treated sample have been systematically characterized by FTIR, thermogravimetric analysis (TGA), XRD, gel permeation chromatography (GPC), a laser particle size analyzer, SEM, an atomic force microscope (AFM), and NMR. The results show that irradiation treatment can partially destroy the intra- or inter-molecular hydrogen bonds of biomass. Irradiation treatment can also reduce particle size, narrow the distribution range, as well as increase the specific surface area of biomasses. Noticeably, the TGA stability of the treated biomass decreases with increasing absorbed doses. To respond to these structural changes, the treated biomass can be easily hydrolyzed by cellulases with a high yield of reducing sugars (557.58 mg/g biomass), much higher than that of the untreated sample. We conclude that irradiation treatment can damage biomass structure, a promising strategy for biomass biorefinery in the future.

Advances in yeast alcoholic fermentations for the production of bioethanol, beer and wine

Yeasts have a long-standing relationship with humankind that has widened in recent years to encompass production of diverse foods, beverages, fuels and medicines. Here, key advances in the field of yeast fermentation applied to alcohol production, which represents the predominant product of industrial biotechnology, will be presented. More specifically, we have selected industries focused in producing bioethanol, beer and wine. In these bioprocesses, yeasts from the genus Saccharomyces are still the main players, with Saccharomyces cerevisiae recognized as the preeminent industrial ethanologen. However, the growing demand for new products has opened the door to diverse yeasts, including non-Saccharomyces strains. Furthermore, the development of synthetic media that successfully simulate industrial fermentation medium will be discussed along with a general overview of yeast fermentation modeling.

Structural and functional characterisation of xylanase purified from Penicillium chrysogenum produced in response to raw agricultural waste

Commercial interest in plant cell wall degrading enzymes (PCWDE) is motivated by their potential for energy or bioproduct generation that reduced dependency on non-renewable (fossil-derived) feedstock. Therefore, underlying work analysed the Penicillium chrysogenum isolate for PCWDE production by employing different biomass as a carbon source. Among the produced enzymes, three xylanase isoforms were observed in the culture filtrate containing sugarcane bagasse. Xylanase (PcX1) presenting 35 kDa molecular mass was purified by gel filtration and anion exchange chromatography. Unfolding was probed and analysed using fluorescence, circular dichroism and enzyme assay methods. Secondary structure contents were estimated by circular dichroism 45% α-helix and 10% β-sheet, consistent with the 3D structure predicted by homology. PcX1 optimally active at pH 5.0 and 30 °C, presenting t_1/2 19 h at 30 °C and 6 h at 40 °C. Thermodynamic parameters/melting temperature 51.4 °C confirmed the PcX1 stability at pH 5.0. PcX1 have a higher affinity for oat spelt xylan, K_M 1.2 mg·mL^-1, in comparison to birchwood xylan K_M 29.86 mg·mL^-1, activity was inhibited by Cu⁺² and activated by Zn⁺². PcX1 exhibited significant tolerance for vanillin, trans-ferulic acid, ρ-coumaric acid, syringaldehyde and 4-hydroxybenzoic acid, activity slightly inhibited (17%) by gallic and tannic acid.

Bacteria-enhanced dilute acid pretreatment of lignocellulosic biomass

Pretreatment is indispensable for the large-scale and low-cost bio-products production from lignocellulosic biomass. Herein, a new bacteria-enhanced dilute acid pretreatment (BE-DAP) strategy was introduced. Cupriavidus basilensis B-8 as a potential bacterium for lignin degradation was employed. Multi-scale characterizations on the physicochemical structure of rice straw indicated that Cupriavidus basilensis B-8 could act on the lignin droplets formed in dilute acid pretreatment (DAP), and dig out these droplets to recover cracks and holes on rice straw surface, leaving an opened and porous structure for the easy access of enzyme to inner cellulose. Eventually, the enzymatic digestibility of RS was increased by 35-70% and 173-244% in BE-DAP compared to DAP pretreated and untreated RS, respectively. The BE-DAP strategy, as well as its physicochemical mechanism, opened new perspectives for lignocellulose pretreatment.

Influence of ozonolysis time during sugarcane pretreatment: Effects on the fiber and enzymatic saccharification

Modifications in sugarcane bagasse (SCB) from ozonolysis (O) NaOH (B) and ultrasound (U) (OBU) treatment for cellulosic ethanol production by enzymatic hydrolysis, were evaluated when increasing the exposure time of SCB to ozone. The lignin, cellulose, and hemicellulose after treatment were quantified: lignin removal and a consequent increase in cellulose content were shown using an infrared spectroscopic technique (ATR-FTIR) and chemical characterization. X-ray diffraction analysis (XRD) proved that OBU treatment does not affect the crystalline cellulose portion and electron microscopy techniques established that the fiber region most affected by the OBU treatment was the secondary cell wall, where the greatest lignin content is located. For OBU-60 treatment the lignin content was reduced and consequently there was a significant increase in cellulose content. After enzymatic hydrolysis, this pretreated SCB released 418mgglucose/g, corresponding to six times more than untreated SCB and a yield of 93% of the cellulose available.

Fractionation for further conversion: from raw corn stover to lactic acid

Fractionation is considered to be one promising strategy to utilize raw biomass to its fullest and produce chemicals with high selectivity. Herein, ethanol/H2O (1/1, v/v) co-solvent with 0.050 M oxalic acid is used to simultaneously fractionate 88.0 wt% of hemicellulose and 89.2 wt% of lignin in corn stover, while cellulose is not obviously degraded. H2O dissolves hemicellulose, G unit and those with β-O-4 linkage of lignin; whereas ethanol extracts G and S units as well as the skeleton with β-5 and β-β linkages of lignin. Oxalic acid effectively catalyzes the hydrolysis of hemicellulose and breaks the intermolecular linkages between hemicellulose and lignin, therefore further promotes the release of lignin. The dissolved hemicelluloses derivatives are reprocessed to produce lactic acid obtaining a high yield of 79.6 wt% with 90% selectivity by the catalysis of MgO. The remained cellulose and recovered lignin can be used further as feedstock to produce chemicals.

Effects of an alkali-acid purification process on the characteristics of eucalyptus lignin fractionated from a MIBK-based organosolv process

In this study, the effects of an alkali-acid purification process on the properties of eucalyptus lignin isolated from a methyl isobutyl ketone (MIBK)/methanol/water-based organosolv fractionation process were evaluated.

Untreated wheat straw: potential source for diverse cellulolytic enzyme secretion by Penicillium janthinellum EMS-UV-8 mutant

Study describes the production of cellulases by Penicillium janthinellum EMS-UV-8 using untreated wheat straw (WS), treated WS (acid, alkali, steam exploded, organo-solv) and pure cellulosic substrates (avicel, cellulose-II and carboxymethyl cellulose). Severely pretreated WS and cellulose-II produced more cellulolytic enzymes than untreated samples. XRD and FTIR analysis revels that the increase in the amorphous structure of pretreated WS/cellulose increases enzyme production. Enzyme samples prepared using different substrates were used for the hydrolysis of dilute acid treated wheat straw (DATWS), steam exploded wheat straw (SEWS) and avicel. The enzyme prepared using untreated WS gave more hydrolysis of DATWS and SEWS than the enzyme prepared using pretreated WS or pure cellulosic substrates. This revels that more diverse/potential enzymes were secreted by P. janthinellum EMS-UV-8 mutant using untreated WS. This study may contribute in production of efficient enzyme mixture/cocktail by single fungal strain for economic conversion of biomass to sugars.

Multi-scale structural and chemical analysis of sugarcane bagasse in the process of sequential acid-base pretreatment and ethanol production by Scheffersomyces shehatae and Saccharomyces cerevisiae

BACKGROUND

Heavy usage of gasoline, burgeoning fuel prices, and environmental issues have paved the way for the exploration of cellulosic ethanol. Cellulosic ethanol production technologies are emerging and require continued technological advancements. One of the most challenging issues is the pretreatment of lignocellulosic biomass for the desired sugars yields after enzymatic hydrolysis. We hypothesized that consecutive dilute sulfuric acid-dilute sodium hydroxide pretreatment would overcome the native recalcitrance of sugarcane bagasse (SB) by enhancing cellulase accessibility of the embedded cellulosic microfibrils.

RESULTS

SB hemicellulosic hydrolysate after concentration by vacuum evaporation and detoxification showed 30.89 g/l xylose along with other products (0.32 g/l glucose, 2.31 g/l arabinose, and 1.26 g/l acetic acid). The recovered cellulignin was subsequently delignified by sodium hydroxide mediated pretreatment. The acid-base pretreated material released 48.50 g/l total reducing sugars (0.91 g sugars/g cellulose amount in SB) after enzymatic hydrolysis. Ultra-structural mapping of acid-base pretreated and enzyme hydrolyzed SB by microscopic analysis (scanning electron microcopy (SEM), transmitted light microscopy (TLM), and spectroscopic analysis (X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, Fourier transform near-infrared (FT-NIR) spectroscopy, and nuclear magnetic resonance (NMR) spectroscopy) elucidated the molecular changes in hemicellulose, cellulose, and lignin components of bagasse. The detoxified hemicellulosic hydrolysate was fermented by Scheffersomyces shehatae (syn. Candida shehatae UFMG HM 52.2) and resulted in 9.11 g/l ethanol production (yield 0.38 g/g) after 48 hours of fermentation. Enzymatic hydrolysate when fermented by Saccharomyces cerevisiae 174 revealed 8.13 g/l ethanol (yield 0.22 g/g) after 72 hours of fermentation.

CONCLUSIONS

Multi-scale structural studies of SB after sequential acid-base pretreatment and enzymatic hydrolysis showed marked changes in hemicellulose and lignin removal at molecular level. The cellulosic material showed high saccharification efficiency after enzymatic hydrolysis. Hemicellulosic and cellulosic hydrolysates revealed moderate ethanol production by S. shehatae and S. cerevisiae under batch fermentation conditions.

Unraveling the structure of sugarcane bagasse after soaking in concentrated aqueous ammonia (SCAA) and ethanol production by Scheffersomyces (Pichia) stipitis

BACKGROUND

Fuel ethanol production from sustainable and largely abundant agro-residues such as sugarcane bagasse (SB) provides long term, geopolitical and strategic benefits. Pretreatment of SB is an inevitable process for improved saccharification of cell wall carbohydrates. Recently, ammonium hydroxide-based pretreatment technologies have gained significance as an effective and economical pretreatment strategy. We hypothesized that soaking in concentrated aqueous ammonia-mediated thermochemical pretreatment (SCAA) would overcome the native recalcitrance of SB by enhancing cellulase accessibility of the embedded holocellulosic microfibrils.

RESULTS

In this study, we designed an experiment considering response surface methodology (Taguchi method, L8 orthogonal array) to optimize sugar recovery from ammonia pretreated sugarcane bagasse (SB) by using the method of soaking in concentrated aqueous ammonia (SCAA-SB). Three independent variables: ammonia concentration, temperature and time, were selected at two levels with center point. The ammonia pretreated bagasse (SCAA-SB) was enzymatically hydrolysed by commercial enzymes (Celluclast 1.5 L and Novozym 188) using 15 FPU/g dry biomass and 17.5 Units of β-glucosidase/g dry biomass at 50°C, 150 rpm for 96 h. A maximum of 28.43 g/l reducing sugars corresponding to 0.57 g sugars/g pretreated bagasse was obtained from the SCAA-SB derived using a 20% v/v ammonia solution, at 70°C for 24 h after enzymatic hydrolysis. Among the tested parameters, pretreatment time showed the maximum influence (p value, 0.053282) while ammonia concentration showed the least influence (p value, 0.612552) on sugar recovery. The changes in the ultra-structure and crystallinity of native SCAA-SB and enzymatically hydrolysed SB were observed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and solid-state (13)C nuclear magnetic resonance (NMR) spectroscopy. The enzymatic hydrolysates and solid SCAA-SB were subjected to ethanol fermentation under separate hydrolysis and fermentation (SHF) and simultaneous saccharification and fermentation (SSF) by Scheffersomyces (Pichia) stipitis NRRL Y-7124 respectively. Higher ethanol production (10.31 g/l and yield, 0.387 g/g) was obtained through SSF than SHF (3.83 g/l and yield, 0.289 g/g).

CONCLUSIONS

SCAA treatment showed marked lignin removal from SB thus improving the accessibility of cellulases towards holocellulose substrate as evidenced by efficient sugar release. The ultrastructure of SB after SCAA and enzymatic hydrolysis of holocellulose provided insights of the degradation process at the molecular level.