Conversion of lignocellulosic biomass to fuels and chemicals has attracted immense research and development around the world. Lowering recalcitrance of biomass in a cost-effective manner is a ...challenge to commercialize biomass-based technologies. Deep eutectic solvents (DESs) are new ‘green' solvents that have a high potential for biomass processing because of their low cost, low toxicity, biodegradability, easy recycling and reuse. This article discusses the properties of DESs and recent advances in their application for lignocellulosic biomass processing. The effectiveness of DESs in hydrolyzing lignin-carbohydrate complexes, removing lignin/hemicellulose from biomass as well as their effect on biomass deconstruction, crystallinity and enzymatic digestibility have been discussed. Moreover, this review presents recent findings on the compatibility of natural DESs with enzymes and microorganisms.
•Physicochemical properties of deep eutectic solvents (DESs) and its application in biomass processing•DESs potential for improved saccharification of biomass and catalytic conversion of sugars into platform molecules•Present approaches for DESs recycling and reuse•Bio-compatibility of DESs with enzymes and microorganisms
Surplus availability of rice straw (RS) presents it as a potential feedstock for ethanol production. Steam explosion (SE) is considered as a green approach to extract fermentable sugars at lower ...cost. The present study deals with the reaction condition optimization for water and dilute acid assisted steam explosion of rice straw at different temperatures and explores the effect of structural properties of solid residue on enzymatic hydrolysis along with mass balance. SE conditions were optimized at pilot scale, raising the temperature from 170 to 200 °C in water assisted SE resulting in an increased glucan conversion from 21.4 to 42.5% at 15% solid loading using 1.5 FPU of cellulases g
–1
biomass. Further, it was improved up to 58.7% by increasing the enzyme dosage to 5 FPU, although it might lead to enhanced enzyme cost by threefold. To reduce costs, small amount of dilute acid (DA) was added during SE and lowering of enzyme consumption i.e. 1.5 FPU/g cellulose has been used to achieve 65.5% glucan conversion. Varying temperature and incorporate dilute acid during pretreatment induced structural alterations in biomass evident by compositional analysis, FT-IR and mass balance. Mass balance study revealed that the overall sugar recovery i.e. 58.7 and 38.8% and theoretical yield of ethanol shall be 222 and 186 L ton
–1
RS respectively, with and without DA addition.
Graphical Abstract
Enzymatic hydrolysis at high solids loading has the potential to reduce both capital and operational expenditures. Here, pretreatment of rice straw (PRS) with dilute acid was carried out at a pilot ...scale (250 kg per day) at 162°C for 10 min and 0.35% acid concentration, followed by enzymatic hydrolysis at different total solids loadings. It showed that although the total sugar concentration increased from 48 to 132 g/l, glucan conversion reduced by 27% (84–66.2%) with increasing solids from 5 to 20% in batch mode. Therefore, two different fed-batch approaches were evaluated to improve the glucan conversion by the sequential addition of a substrate and/or enzyme. At 20% solid loadings and a 3 filter paper units/g enzyme dosage, the highest glucan conversion obtained was 66% after 30 h of hydrolysis in batch mode. However, in an optimized fed-batch approach, the glucan yield was improved to 70% by simply dividing the substrate feeding into three batches, that is, 50% at 0 h, 25% each after 4 h, and 8 h of hydrolysis reaction. The addition of surfactant (Ecosurf E6) further improved the conversion to 72% after 30 h. The role of critical factors, that is, inhibitors, enzyme–lignin binding, and viscosity, was investigated during the course of hydrolysis in the batch and fed-batch approaches. This study suggests a sustainable approach for improved hydrolysis at high solids loadings by fine-tuning a simple process.
Multiple enzymes are required for efficient hydrolysis of lignocellulosic biomass and no wild type organism is capable of producing all enzymes in desired levels. In this study, steam explosion of ...wheat straw was carried out at pilot scale and a synthetic enzyme mixture (EnzMix) was developed by partially replacing the cellulase with critical dosages of commercially available accessory enzymes (β-glucosidase, xylanase and laccase) through central composite design. Highest degree of synergism (DS) was observed with β-glucosidase (1.68) followed by xylanase (1.36). Finally, benchmarking of EnzMix (Celluclast, β-glucosidase and xylanase in a protein ratio of 20.40: 38.43: 41.16, respectively) and other leading commercial enzymes was carried out. Interestingly, hydrolysis improved by 75% at 6 h and 30% at 24 h, respectively in comparison of control. By this approach, 25% reduction in enzyme dosage was observed for obtaining the same hydrolysis yield with opitimized enzyme cocktail. Thus, development of enzyme cocktail is an effective and sustainable approach for high hydrolysis efficiency.
Second-generation bioethanol production by a newly isolated thermotolerant yeast strain was studied at 42 degree C and above using pilot-scale dilute acid pretreated wheat straw (WS) as feedstock. ...This strain was identified as Kluyveromyces marxianus DBTIOC-35 by biochemical characterization as well as molecular phylogenetic analysis of the ITS-5.8S rRNA gene and D1/D2 domain of the 26S rRNA gene after PCR amplification and sequencing. Simultaneous saccharification and fermentation (SSF) at 42 degree C and 45 degree C using 10% biomass loading resulted in ethanol titers of 29.0 and 16.1 g L super(-1), respectively. At 42 degree C ethanol productivity was higher during SSF (0.92 g L super(-1) h super(-1)) than separate hydrolysis and fermentation (SHF) (0.49 g L super(-1) h super(-1)) at 20% biomass loading. The results indicated that at 20% biomass loading, SSF without pre-saccharification led to more ethanol production (66.2 g L super(-1) with 83.3% yield) at a faster rate than SSF with pre-saccharification (PSSF) which produced an ethanol titer of 61.8 g L super(-1), 77.7% yield and productivity of 0.86 g L super(-1) h super(-1). Based on these findings, application of newly isolated yeast K. marxianus DBTIOC-35 in SSF of lignocellulosic biomass can eliminate the pre-saccharification step which is a novel advantage of thermotolerant yeasts in terms of cutting down the overall biomass to bioethanol process time and enhancing bioethanol titer, yields and productivities.
A variety of bacterial strains were isolated from waste disposal sites of Uttaranchal, India, and some from artificially developed soil beds containing maleic anhydride, glucose, and small pieces of ...polyethylene. Primary screening of isolates was done based on their ability to utilize high- and low-density polyethylenes (HDPE/LDPE) as a primary carbon source. Thereafter, a consortium was developed using potential strains. Furthermore, a biodegradation assay was carried out in 500-ml flasks containing minimal broth (250 ml) and HDPE/ LDPE at 5 mg/ml concentration. After incubation for two weeks, degraded samples were recovered through filtration and subsequent evaporation. Fourier transform infrared spectroscopy (FTIR) and simultaneous thermogravimetric-differential thermogravimetry-differential thermal analysis TG-DTG-DTA) were used to analyze these samples. Results showed that consortium-treated HDPE (considered to be more inert relative to LDPE) was degraded to a greater extent 22.41% weight loss) in comparison with LDPE (21.70% weight loss), whereas, in the case of untreated samples, weight loss was more for LDPE than HDPE (4.5% and 2.5%, respectively) at 400 degrees . Therefore, this study suggests that polyethylene could be degraded by utilizing microbial consortia in an eco-friendly manner.
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•21 surfactants evaluated for the impact on pretreated biomass saccharification.•Selected surfactant enhanced saccharification of steam exploded biomass by 55% and dilute acid ...pretreated biomass by 26%.•Mechanism of surfactant action investigated.•Surfactant supplementation is an effective strategy to achieve higher saccharification and reducing enzyme dosage.
In this study, commercial surfactants have been investigated at economically viable dosage to enhance the enzymatic saccharification of pretreated wheat straw at high solid loadings. Twenty one surfactants were evaluated with pilot scale pretreated wheat straw and mechanism of surfactant action has been elucidated. One surfactant has improved the saccharification of dilute acid wheat straw (DAWS) by 26.4% after 24h and 23.1% after 48h while, steam exploded wheat straw (SEWS) saccharification was increased by 51.2% after 24h and 36.4% after 48h at 10% solid loading. At 20% solid loading, about 31% increase in yield was obtained on DAWS and about 55% on SEWS after 48h. Further, lignin was isolated from pretreated wheat straws and characterized which revealed that SEWS derived lignin was more hydrophobic than DAWS lignin. This investigation suggests that surfactant supplementation during saccharification is an effective strategy to achieve higher saccharification yield.
Rapid industrialization, improved standards of living, growing economies and ever-increasing population has led to the unprecedented exploitation of the finite and non-renewable resources of minerals ...in past years. It was observed that out of 100 BMT of raw materials processed annually only 10% is recycled back. This has resulted in a strenuous burden on natural or primary resources of minerals (such as ores) having limited availability. Moreover, severe environmental concerns have been raised by the huge piles of waste generated at landfill sites. To resolve these issues, ‘Urban Mining’ from waste or secondary resources in a Circular Economy’ concept is the only sustainable solution. The objective of this review is to critically examine the availability, elemental composition, and the market potential of the selected secondary resources such as lignocellulosic/algal biomass, desalination water, sewage sludge, phosphogypsum, and e-waste for minerals sequestration. This review showed that, secondary resources have potential to partially replace the minerals required in different sectors such as macro and microelements in agriculture, rare earth elements (REEs) in electrical and electronics industry, metals in manufacturing sector and precious elements such as gold and platinum in ornamental industry. Further, inputs from the selected life cycle analysis (LCA) & techno economic analysis (TEA) were discussed which showed that although, urban mining has a potential to reduce the greenhouse gaseous (GHG) emissions in a sustainable manner however, process improvements through innovative, novel and cost-effective pathways are essentially required for its large-scale deployment at industrial scale in future.
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We discuss how rapid industrialization, improved standards of living, growing economies and ever-increasing population has led to the unprecedented exploitation of the finite and non-renewable ...resources of minerals in past years. It was observed that out of 100 BMT of raw materials processed annually only 10% is recycled back. This has resulted in a strenuous burden on natural or primary resources of minerals (such as ores) having limited availability. Moreover, severe environmental concerns have been raised by the huge piles of waste generated at landfill sites. To resolve these issues, ‘Urban Mining’ from waste or secondary resources in a Circular Economy’ concept is the only sustainable solution. The objective of this review is to critically examine the availability, elemental composition, and the market potential of the selected secondary resources such as lignocellulosic/algal biomass, desalination water, sewage sludge, phosphogypsum, and e-waste for minerals sequestration. This review showed that, secondary resources have potential to partially replace the minerals required in different sectors such as macro and microelements in agriculture, rare earth elements (REEs) in electrical and electronics industry, metals in manufacturing sector and precious elements such as gold and platinum in ornamental industry. Further, inputs from the selected life cycle analysis (LCA) & techno economic analysis (TEA) were discussed which showed that although, urban mining has a potential to reduce the greenhouse gaseous (GHG) emissions in a sustainable manner however, process improvements through innovative, novel and cost-effective pathways are essentially required for its large-scale deployment at industrial scale in future.
Rapid Detection of Cadmium-Resistant Plant Growth Promotory Rhizobacteria: A Perspective of ELISA and QCM-Based Immunosensor Agrawal, Ruchi, CBSH, GB Plant University of Agriculture and Technology, Pantnagar, Uttarakhand, India; Satlewal, Alok, CBSH, GB Plant University of Agriculture and Technology, Pantnagar, Uttarakhand, India; Chaudhary, Manav, CBSH, GB Plant University of Agriculture and Technology, Pantnagar, Uttarakhand, India ...
Journal of microbiology and biotechnology,
06/2012, Letnik:
22, Številka:
6
Journal Article
Recenzirano
Plant growth-promoting rhizobacteria (PGPR) pseudomonads have a large number of lipopolysaccharides on the cell surface, which induces immune responses. Cd-resistant PGPR prevalent at the Cd-affected ...sites under biophytostabilization was monitored. Transmissiom electron microscopy was used to the study the behavior of tolerance of PGPR to cadmium level and its effect on pseudomonad strains (Z9, S2, KNP2, CRPF, and NBRI). An immunosensor was developed by immobilizing antibody (anti-Z9 or anti-S2) against selected PGPR on a piezoelectric quartz crystal microbalance (QCM). Immunosensors were found to supplement the inherent specificity of antigen antibody reactions with the high sensitivity of a physical transducer. On comparison of the efficiency of detection with ELISA, the spectrophotometric technique, the developed immunosensor was found to be more sensitive, fast, and reliable even after regeneration for several times. Thus, the immunosensor may be used for future detection of PGPR strains after automation of the screening process.
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