A concerted enzymatic de-structuring of lignocellulosic materials using a compost-derived microbial consortia favoring the consolidated pretreatment and bio-saccharification

The robustness of microbial consortia isolated from compost habitat encompasses the complementary metabolism that aids in consolidated bioprocessing (CBP) of lignocellulosic biomass (LCB) by division of labor across the symbionts. Composting of organic waste is deemed to be an efficient way of carbon recycling, where the syntrophic microbial population exerts a concerted action of lignin and polysaccharide (hemicellulose and cellulose) component of plant biomass. The potential of this interrelated microorganism could be enhanced through adaptive laboratory evolution (ALE) with LCB for its desired functional capabilities. Therefore, in this study, microbial symbionts derived from organic compost was enriched on saw dust (SD) (woody biomass), aloe vera leaf rind (AVLR) (agro-industrial waste) and commercial filter paper (FP) (pure cellulose) through ALE under different conditions. Later, the efficacy of enriched consortium (EC) on consolidated pretreatment and bio-saccharification was determined based on substrate degradation, endo-enzymes profiling and fermentable sugar yield. Among the treatment sets, AVLR biomass treated with EC-5 has resulted in the higher degradation rate of lignin (47.01 ± 0.66%, w/w) and polysaccharides (45.87 ± 1.82%, w/w) with a total sugar yield of about 60.01 ± 4.24 mg/g. In addition, the extent of structural disintegration of substrate after EC-treatment was clearly deciphered by FTIR and XRD analysis. And the factors of Pearson correlation matrix reinforces the potency of EC-5 by exhibiting a strong positive correlation between AVLR degradation and the sugar release. Thus, a consortium based CBP could promote the feasibility of establishing a sustainable second generation biorefinery framework.

Enzymatically triggered delignification through a novel stable laccase: A mixed in-silico /in-vitro exploration of a complex environmental microbiota

Laccases have been broadly applied as a multitasking biocatalyst in various industries, but their applications tend to be limited by easy deactivation, lack of adequate stability, and susceptibility under complex conditions. Identifying stable laccase as a green-biocatalyst is crucial for developing cost-effective biorefining processes. In this direction, we attempted in-silico screening a stable metagenome-derived laccase (PersiLac1) from tannery wastewater in a complex environment. The laccase exhibited high thermostability, retaining 53.19% activity after 180 min at 70 °C, and it was stable in a wide range of pH (4.0-9.0). After 33 days of storage at 50°C, pH 6.0, the enzyme retained 71.65% of its activity. Various metal ions, inhibitors, and organic solvents showed that PersiLac1 has a stable structure. The stable PersiLac1 could successfully remove lignin and phenolic from quinoa husk and rice straw. In the separate hydrolysis and fermentation process (SHF) after 72 h, hydrolysis was obtained 100% and 73.4% for quinoa husk and rice straw, and fermentation by the S. cerevisiae was be produced 41.46 g/L and 27.75g/L ethanol, respectively. Results signified that the novel lignin-degrading enzyme was confirmed to have great potential for industrial application as a green-biocatalyst based on enzymatically triggered to delignification and detoxify lignocellulosic biomass.

Green route for recycling of low-cost waste resources for the biosynthesis of nanoparticles (NPs) and nanomaterials (NMs)-A review

Nowadays, nanoparticles (NPs) and nanomaterials (NMs) are used extensively in various streams such as medical science, solar energy, drug delivery, water treatment, and detection of persistent pollutants. Intensive synthesis of NPs/NMs carried out via physico-chemical technologies is deteriorating the environment globally. Therefore, an urgent need to adopt cost-effective and green technologies to synthesize NPs/NMs by recycling of secondary waste resources is highly required. Environmental wastes such as metallurgical slag, electronics (e-waste), and acid mine drainage (AMD) are rich sources of metals to produce NPs. This concept can remediate the environment on the one hand and the other hand, it can provide a future roadmap for economic benefits at industrial scale operations. The waste-derived NPs will reduce the industrial consumption of limited primary resources. In this review article, green emerging technologies involving lignocellulosic waste to synthesize the NPs from the waste streams and the role of potential microorganisms such as microalgae, fungi, yeast, bacteria for the synthesis of NPs have been discussed. A critical insight is also given on use of recycling technologies and the incorporation of NMs in the membrane bioreactors (MBRs) to improve membrane functioning and process performance. Finally, this study aims to mitigate various persisting scientific and technological challenges for the safe disposal and recycling of organic and inorganic waste for future use in the circular economy.

Biochemical Characterization of Cellulase From Bacillus subtilis Strain and its Effect on Digestibility and Structural Modifications of Lignocellulose Rich Biomass

Microbial cellulases have become the mainstream biocatalysts due to their complex nature and widespread industrial applications. The present study reports the partial purification and characterization of cellulase from Bacillus subtilis CD001 and its application in biomass saccharification. Out of four different substrates, carboxymethyl cellulose, when amended as fermentation substrate, induced the highest cellulase production from B. subtilis CD001. The optimum activity of CMCase, FPase, and amylase was 2.4 U/ml, 1.5 U/ml, and 1.45 U/ml, respectively. The enzyme was partially purified by (NH₄)₂SO₄ precipitation and sequenced through LC-MS/MS. The cellulase was found to be approximately 55 kDa by SDS-PAGE and capable of hydrolyzing cellulose, as confirmed by zymogram analysis. The enzyme was assigned an accession number AOR98335.1 and displayed 46% sequence homology with 14 peptide-spectrum matches having 12 unique peptide sequences. Characterization of the enzyme revealed it to be an acidothermophilic cellulase, having an optimum activity at pH 5 and a temperature of 60°C. Kinetic analysis of partially purified enzyme showed the Km and Vmax values of 0.996 mM and 1.647 U/ml, respectively. The enzyme activity was accelerated by ZnSO_4, MnSO_4, and MgSO_4, whereas inhibited significantly by EDTA and moderately by β-mercaptoethanol and urea. Further, characterization of the enzyme saccharified sugarcane bagasse, wheat straw, and filter paper by SEM, ATR-FTIR, and XRD revealed efficient hydrolysis and structural modifications of cellulosic materials, indicating the potential industrial application of the B. subtilis CD001 cellulase. The findings demonstrated the potential suitability of cellulase from B. subtilis CD001 for use in current mainstream biomass conversion into fuels and other industrial processes.

A comparative study of greener alternatives for nanocellulose production from sugarcane bagasse

Use of enzyme for extraction of nanocellulose from sugarcane bagasse is greener alternative. Literature indicates that effectiveness of these enzymes can be improved by auxiliary enzymes or mediators. In the current study, extraction of nanocellulose using laccase with these moderators, auxiliary enzyme glucose oxidase and mediator molecule, ABTS [2,2'-azinobis(3-ethylbenzthiazoline-6-sulfonate)] individually was done. Cellulose and lignin content, FT-IR, TGA and DSC analysis, XRD, SEM and PSA were done. Enzyme moderators improved the performance of laccase in lignin degradation. Lignin and cellulose content, crystallinity were used as parameters to optimize the concentrations, which was found to be ABTS (at 1.4 mM) and glucose oxidase (at 0.15 mg ml-1). At the optimal concentration, nanocellulose was extracted. Properties of nanocellulose obtained from both routes were compared. Size analysis revealed 339 nm and 636 nm for nanocellulose obtained with glucose oxidase and ABTS, respectively. Defibrillation was better in the case of the former one as seen from SEM.

Laccase-mediated delignification and detoxification of lignocellulosic biomass: removing obstacles in energy generation

The rising global population and worldwide industrialization have led to unprecedented energy demand that is causing fast depletion of fossil reserves. This has led to search for alternative energy sources that are renewable and environment friendly. Use of lignocellulosic biomass for energy generation is considered a promising approach as it does not compete with food supply. However, the lignin component of the biomass acts as a natural barrier that prevents its efficient utilization. In order to remove the lignin and increase the amount of fermentable sugars, the lignocellulosic biomass is pretreated using physical and chemical methods which are costly and hazardous for environment. Moreover, during the traditional pretreatment process, numerous inhibitory compounds are generated that adversely affect the growth of fermentative microbes. Alternatively, biological methods that use microbes and their enzymes disrupt lignin polymers and increase the accessibility of the carbohydrates for the sugar generation. Microbial laccases have been considered as an efficient biocatalyst for delignification and detoxification offering a green initiative for energy generation process. The present review aims to bring together recent studies in bioenergy generation using laccase biocatalyst in the pretreatment processes. The work provides an overview of the sustainable and eco-friendly approach of biological delignification and detoxification through whole-cell and enzymatic methods, use of laccase-mediator system, and immobilized laccases for this purpose. It also summarizes the advantages, associated challenges, and potential prospects to overcome the limitations.

Recent nanobiotechnological advancements in lignocellulosic biomass valorization: A review

Increase in human population, rapid industrialization, excessive utilization of fossil fuel utilization and anthropogenic activities have caused serious threats to the environment in terms of greenhouse gas emissions (GHGs), global warming, air pollution, acid rain, etc. This destruction in sustainability can be averted by a paradigm shift in the fuel production from fossil resources to bioenergy. Amongst different forms of bioenergy, lignocellulosic biomass can be utilized as an attractive substrate for the production of several high-value products owing to its renewability, easy availability, and abundance. Additionally, utilization of these waste biomasses reduces the environmental hazards associated with its disposal. Impedance of lignin and crystalline nature of cellulose pose major bottlenecks in biomass based energy. Though, several physio-chemicals processes are recommended as mitigation route but none of them seems to be promising for large scale application. In recent years, a right fusion of biological treatment combined with nanotechnology for efficient pretreatment and subsequent hydrolysis of biomass by ubiquitous enzymes seems to be promising alternative. In addition, to overcome these difficulties, nanotechnology-based methods have been recently adopted in catalytic valorization of lignocellulosic biomass. The present review has critically discussed the application of nano-biotechnology in lignocellulosic biomass valorization in terms of pretreatment and hydrolysis. A detailed discussion on the application of various nanoparticles in these processes, enzyme immobilization and end-production utilization is presented in this review. Finally, the review emphasizes the major challenges of this process along with different routes and recommendations to address the issues.

Studies on laccase mediated conversion of lignin from ginseng residues for the production of sugars

The purpose of this study was to determine the production of sugars from ginseng residues treated with laccase. Laccase was used to degrade lignin from ginseng residues in order to increase the yield of sugars. Reaction conditions, including solid loading, pH, enzyme concentration, incubation temperature, and incubation time, were investigated and optimized. The results showed that the optimum conditions were 20% of solid loading (w/v), pH 7, 300 IU/ml, temperature of 40 °C and incubation time of 6 h. The minimum residual lignin obtained was 59.89%. The results also showed that 56.58% sugars including 12.04% water soluble polysaccharides (WSP), 16.24% water insoluble polysaccharides (WIP) and 5.08% reducing sugar were afforded from delignify substance. Chemical characters of these sugars were analyzed. Pretreat of laccase delignification for sugars production is expected to be applied to other herbal residues.

Valorization of sugarcane bagasse by chemical pretreatment and enzyme mediated deconstruction

After chemical pretreatment, improved amenability of agrowaste biomass for enzymatic saccharification needs an understanding of the effect exerted by pretreatments on biomass for enzymatic deconstruction. In present studies, NaOH, NH₄OH and H₂SO₄ pretreatments effectively changed visible morphology imparting distinct fibrous appearance to sugarcane bagasse (SCB). Filtrate analysis after NaOH, NH₄OH and H₂SO₄ pretreatments yielded release of soluble reducing sugars (SRS) in range of ~0.17–0.44%, ~0.38–0.75% and ~2.9–8.4% respectively. Gravimetric analysis of pretreated SCB (PSCB) biomass also revealed dry weight loss in range of ~25.8–44.8%, ~11.1–16.0% and ~28.3–38.0% by the three pretreatments in the same order. Release of soluble components other than SRS, majorly reported to be soluble lignins, were observed highest for NaOH followed by H₂SO₄ and NH₄OH pretreatments. Decrease or absence of peaks attributed to lignin and loosened fibrous appearance of biomass during FTIR and SEM studies respectively further corroborated with our observations of lignin removal. Application of commercial cellulase increased raw SCB saccharification from 1.93% to 38.84%, 25.56% and 9.61% after NaOH, H₂SO₄ and NH₄OH pretreatments. Structural changes brought by cell wall degrading enzymes were first time shown visually confirming the cell wall disintegration under brightfield, darkfield and fluorescence microscopy. The microscopic evidence and saccharification results proved that the chemical treatment valorized the SCB by making it amenable for enzymatic saccharification.

Laccase mediated delignification of pineapple leaf waste: an ecofriendly sustainable attempt towards valorization

Background

Escalating energy security, burgeoning population and rising costs of fossil fuels have focussed our attention on tapping renewable energy sources. As the utilization of food crops for biofuel production culminates into food vs. fuel dilemma, there is an intensive need for alternatives. Production of biofuels from lignocellulosic biomass owing to its profuse availability and high holocellulose content is a promising area for research.

Results

In the present study, pineapple leaf, an agro-industrial waste was pretreated with laccase to enhance the enzymatic digestibility of the substrate for improved production of reducing sugar. Variables determining enzymatic delignification of pineapple leaf waste have been optimized by response surface methodology based on central composite design. Maximum delignification of 78.57%(w/w) resulted in reducing sugar of 492.33 ± 3.1 mg/g in 5.30 h. The structural changes in pineapple leaf waste, after laccase treatment, were studied through Fourier transformed infrared spectroscopy, X-ray diffraction and Scanning electron microscopy. Specific surface area, pore volume, and pore diameter of the substrate were studied using the Brunauer–Emmett–Teller and Barrett–Joyner–Halenda methods and found a significant increase in the aforementioned parameters after delignification.

Conclusion

Laccase mediated delignification of pineapple leaf waste is a cleaner sustainable process for enhanced production of reducing sugar which can accomplish the demand for biofuels.

In silico optimization of enzyme mediated debittering of Assam lemon: biochemical and sensory evaluation studies

Commercialization of citrus fruit juice is always hindered by the bitterness development in juice when stored for a significant period of time. In order to debitter citrus juice, an attempt has been taken up by treating the juice with tannase. Central Composite Design (CCD) based Response Surface Methodology (RSM) has been implemented to evaluate and optimize the effect of underlying process parameters viz., enzyme volume, temperature, incubation time and enzyme titre on debittering effect of Assam lemon juice. The significance of parameters and their interaction were assessed by analysis of variance at 95% level of confidence. Optimization study reveals that the maximum debittering (40.12 ± 0.02%) of Assam lemon juice takes place at ambient temperature (37 °C) within an incubation time of 2 h and 1.12% (v/v) enzyme volume while 30 IU/ml enzyme activity. Moreover, percentage contribution of the underlying process parameters demonstrate that the enzyme volume and enzyme titre as first and second most significant contributors in process of debittering. As part of validating the above results, experimental debittering has been performed and compared with predicted debittering percentage which showed a high coefficient value (0.971) which ensures the effectiveness of the proposed model. Biochemical analysis of the treated juice reveals improved antioxidant property after enzymatic treatment by 15.30%. Total sugar and reducing sugar content has also been enhanced by 1.38 and 1.49 folds, respectively, after enzymatic treatment of juice. Furthermore, no alteration in the elemental composition of the treated juice ensure that the quality of the final juice is retained with the enzyme applications. Sensory analysis based on nine-point Hedonic scale advocates the best organoleptic property in 1% (v/v) enzyme treated juice.

Partially consolidated bioprocessing of mixed lignocellulosic feedstocks for ethanol production

Rapid urbanization and industrialization have accelerated the energy demand which cannot be met by decreasing fossil fuels thereby substantiate the need for lignocellulosic ethanol. The present study is one such attempt towards bioethanol production in an eco-friendly manner using enzymes in which a mixture of lignocellulosic biomass namely, Ricinus communis, Saccharum officinarum (tops) and Saccharum spontaneum were taken as a substrate. The mixed biomass was processed through partially consolidated bioprocessing (PCBP) approach which involves a non-isothermal simultaneous pretreatment and saccharification step where a concoction of laccase (Pleurotus djamor) and holocellulase (Trichoderma reseei RUT C30) was used followed by co-fermentation within the same reactor. The process parameters influencing PCBP were optimized using feed-forward ANN model which resulted in a maximum ethanol concentration of 7.86% (v/v) (62.01g/L) at pentose to hexose strain ratio of 0.696 (v/v), substrate loading of 27.54% (w/v) and incubation time of 21.96h.

Enantioselective Syntheses of Lignin Models: An Efficient Synthesis of β-O-4 Dimers and Trimers by Using the Evans Chiral Auxiliary

We describe an efficient five-step, enantioselective synthesis of (R,R)- and (S,S)-lignin dimer models possessing a β-O-4 linkage, by using the Evans chiral aldol reaction as a key step. Mitsunobu inversion of the (R,R)- or (S,S)-isomers generates the corresponding (R,S)- and (S,R)-diastereomers. We further extend this approach to the enantioselective synthesis of a lignin trimer model. These lignin models are synthesized with excellent ee (>99 %) and high overall yields. The lignin dimer models can be scaled up to provide multigram quantities that are not attainable by using previous methodologies. These lignin models will be useful in degradation studies probing the selectivity of enzymatic, microbial, and chemical processes that deconstruct lignin.

Enzyme mediated biomass pretreatment and hydrolysis: a biotechnological venture towards bioethanol production

Biobased processes are gaining major interest worldwide with considerable efforts now being applied to developing efficient technologies for bioresource utilization.

Direct hydrogen production from lignocellulose by the newly isolated Thermoanaerobacterium thermosaccharolyticum strain DD32

The comparison of hydrogen production by conventional process and consolidated bioprocessing.