Treatment and resource recovery options for first and second generation bioethanol spentwash - A review

Impact of short-term irrigation of diverse distillery wastewater types on plant attributes and antioxidative enzymes of pea (Pisum sativum L. var. Rachna)

The study was focused on evaluating the short-term irrigation effect of three different types of distillery wastewater, i.e., untreated, primary treated, and secondary treated, on the germination, growth, photosynthetic pigments, and antioxidant enzymes of pea (Pisum sativum L. var. Rachna). The findings indicated that exposure to 50% secondary treated distillery wastewater (ST50) resulted in the maximum values for positive germination parameters of pea, including germination percentage, germination value, germination index, peak value, vigor index, speed of germination, and tolerance index. The minimum values were observed at 100% concentration of untreated wastewater (UT100). In contrast, the maximum values for various negative germination parameters, i.e., percent inhibition, seedling mortality, and germination period, were observed at UT100 and minimum at ST50. All the growth parameters studied, i.e., length of shoot, length of root and length of seedlings, fresh weight of shoot, fresh weight of root, dry weight of shoot, and dry weight of root, showed maximum values at ST50 and minimum at UT100. Photosynthetic pigment analysis also followed a similar trend. The antioxidative enzyme characterization of Pisum sativum L. var. Rachna revealed the minimum values of catalase, ascorbic peroxidase, glutathione reductase, and superoxide dismutase at ST25 (25% concentration of secondary treated distillery wastewater) and maximum values were observed at UT100.

Microalgae on distillery wastewater treatment for improved biodiesel production and cellulose nanofiber synthesis: A sustainable biorefinery approach

Sugarcane spent wash generates waste at a large scale that impacts the environment, hence the classic waste reuse technology needs to be implemented. An integrated approach of spent wash and microalgae cultivation to produce biodiesel has gained momentum in recent times. However, the microalgae technology lacks the functional utilization of de-oiled microalgae biomass (DOB). This study proposed the development of a microalgae-based advanced process for distillery spent wash treatment, biomass recovery for biodiesel and utilizing algal residue as a step towards waste management. A novel microalga Coelastrella sp KJ-04 grown in distillery spent wash represented with high biomass (4.61g/L) and lipid production (3.6 g/L). The significant reduction in Chemical Oxygen Demand (COD, 49.3%), Total Nitrogen (TN, 49.7%), Total Phosphorous (TP, 21.8%), Total Organic Carbon (TOC, 40.2%), Total Sulphur (S, 37.2%) and Potassium (K, 42.5%) were achieved in spent wash. The extracted lipids of Coelastrella sp KJ-04 were converted to Fatty acid methyl ester (FAME) and examined by Gas chromatography -mass spectrometry (GC-MS) to observe the suitability for biodiesel prospect. The de-oiled biomass (DOB) was utilized for the synthesis of Cellulose nanofibers (CNF), purified and estimated with a diameter ranging between 20 and 27 nm. The crystalline structure and functional group of CNF were analyzed by X-ray diffraction (XRD) and Fourier Transform infrared spectroscopy (FTIR). The unprecedented work demonstrated the microalgae biorefinery approach for spent wash remediation, biodiesel synthesis and simultaneous production of biodegradable CNF from algal residue to support waste-free technology. In future, CNF can be reinforced into material for concrete as it could be the smart alternative to replace synthetic cement plastics.

Valorization of wastewater to recover value-added products: A comprehensive insight and perspective on different technologies

In recent years, due to rapid globalization and urbanization, the demand for fuels, energy, water and nutrients has been continuously increasing. To meet the future need of the society, wastewater is a prominent and emerging source for resource recovery. It provides an opportunity to recover valuable resources in the form of energy, fertilizers, electricity, nutrients and other products. The aim of this review is to elaborate the scientific literature on the valorization of wastewater using wide range of treatment technologies and reduce the existing knowledge gap in the field of resource recovery and water reuse. Several versatile, resilient environmental techniques/technologies such as ion exchange, bioelectrochemical, adsorption, electrodialysis, solvent extraction, etc. are employed for the extraction of value-added products from waste matrices. Since the last two decades, valuable resources such as polyhydroxyalkanoate (PHA), matrix or polymers, cellulosic fibers, syngas, biodiesel, electricity, nitrogen, phosphorus, sulfur, enzymes and a wide range of platform chemicals have been recovered from wastewater. In this review, the aspects related to the persisting global water issues, the technologies used for the recovery of different products and/or by-products, economic sustainability of the technologies and the challenges encountered during the valorization of wastewater are discussed comprehensively.

Four stroke diesel engine performance and emission studies of ethanol recovered from Kappaphycus alvarezii reject -solid food waste mixed substrates and its blends

Bioethanol is an eco-friendly green fuel, owing to its production from sustainable bio-based sources. In this study, bioethanol (BE) is produced from Kappaphycus alverezii reject (KR) blended with Solid Food Waste (SFW). This bioethanol is blended with petroleum-based diesel (PBD) in the following proportions: 15%, 20% and 25% for further studies. Performance characteristics, specifically Brake Specific Fuel Consumption (BSFC), Brake Thermal Efficiency (BTE), Brake Power (BP) and exhaust emissions, mainly Carbon monoxide (CO), Carbon dioxide (CO₂), Smoke Opacity (SO), hydrocarbons (HC) and oxides of Nitrogen (NO_X) have been investigated. The blended test fuels show better results, which is confirmed by the performance characteristics of BTE being lower than PBD. The emission report shows lesser CO (0.12%) and SO (59.6%) compared to PBD (0.14% and 67.2%), signifying the clean-burning tendency of BE blends. From the findings, PBD75: BE25 is an excellent fuel blend for improving flow properties, engine performance, and emission characteristics.

Sustainable bioconversion of potato peel wastes into ethanol and biogas using organosolv pretreatment

Potato processing industries generate considerable amounts of residues, i.e., potato peel wastes (PPW). Valorization of PPW for bioethanol and biogas production via a biorefining process was investigated in this study. Organosolv pretreatment was performed on the PPW using 50-75% (v/v) ethanol solution at 120-180 °C with/without the presence of 1% (w/w) H₂SO₄ (as a catalyst). After the pretreatment, the solvent, i.e., ethanol, was recovered by distillation. Catalyzed organosolv pretreatment using 50% (v/v) ethanol at 120 °C followed by enzymatic hydrolysis resulted in a high hydrolysate yield of 539.8 g glucose/kg dry PPW that was successfully fermented to 224.2 g ethanol/kg dry PPW. To recover more energy, the liquid fraction of the pretreatment remained after solvent recovery and the unhydrolyzed solids that remained from the enzymatic hydrolysis were anaerobically digested. From each kg of dry PPW, the anaerobic digestion produced 57.9 L biomethane. Thus, the biorefinery comprising ethanolic organosolv pretreatment, solvent recovery, enzymatic hydrolysis, ethanolic fermentation, and anaerobic digestion of residues was produced 8112 kJ energy per kg of dry PPW.

A critical review of advanced nanotechnology and hybrid membrane based water recycling, reuse, and wastewater treatment processes

One of the modern challenges is to provide clean and affordable drinking water. Water scarcity is caused by the growing population in the world and pollutants contaminate all remaining water sources. Innovative water treatment solutions have been provided by nanotechnology. Microorganisms, organic suspensions, and inorganic heavy metal ions, among other things, are common water contaminants. Since antiquity, a wide range of water clean-up methods have been employed to address this issue. Breakthroughs in water purification procedures have occurred during the previous four decades, with the most significant one being the use of nanomaterials and nanomembranes. Nanoparticles and nanomembranes (polymeric membranes) have recently been used in engineered materials (TiO₂, ZnO, CuO, Ag, CNT's and mixed oxide nanoparticles, for example). Engineered nanomembranes, nanocomposites and nanoparticles have been used in this review article's discussion of water purification technologies. The review also discusses the risk and solutions of using nanoparticles and nanocomposites in the future.

On the functionality of the N-terminal domain in xylanase 10A from Ruminococcus albus 8

We analyzed the structure to function relationships in Ruminococcus albus 8 xylanase 10A (RalXyn10A) finding that the N-terminus 34-amino acids sequence (N34) in the protein is particularly functional. We performed the recombinant wild type enzyme's characterization and that of the truncated mutant lacking the N34 extreme (RalΔN34Xyn10A). The truncated enzyme exhibited about half of the activity and reduced affinity for binding to insoluble saccharides. These suggest a (CBM)-like function for the N34 motif. Besides, RalXyn10A activity was diminished by redox agent dithiothreitol, a characteristic absent in RalΔN34Xyn10A. The N34 sequence exhibited a significant similarity with protein components of the ABC transporter of the bacterial membrane, and this motif is present in other proteins of R. albus 8. Data suggest that N34 would confer RalXyn10A the capacity to interact with polysaccharides and components of the cell membrane, enhancing the degradation of the substrate and uptake of the products by the bacterium.

Partial consolidated bioprocessing of pretreated Pennisetum sp. by anaerobic thermophiles for enhanced bioethanol production

Rapid industrialization and consumption of fossil fuels have led to considerable progress in the production of renewable biofuels like bioethanol. Lignocellulosic biomass such as grasses serves as cheap feedstocks for the production of bioethanol. However, the process involved in lignocellulosic bioethanol production is expensive which restricts its industrial production. The present study thus attempted to investigate a partially consolidated bioprocessing (PCB) approach using two isolated anaerobic thermophiles i.e. Bacillus paranthracis and Bacillus nitratireducens for direct conversion of ultra-sonication assisted sodium hydroxide (UA-NaOH) pretreated Denannath grass to bioethanol in co-culture consortium batch fermentation experiments. The process parameters for the PCB approach were optimized using the Box-Behnken design of Response Surface Methodology (RSM). The parameters that were considered were substrate concentration (5-10 g), incubation time (30-66 h), inoculum volume [1:1 to 3:3 (% v/v) and temperature (50-65 °C). The maximum ethanol concentration of 8.46 mM (0.39 g/L from 7.5 g/L of substrate loading) and ethanol yield (Yp/s) of 0.55 g/g of reducing sugar was obtained at 57.5 °C. In the same conditions the cellulase and xylanase activities were 0.8 U/mL and 11.53 U/mL respectively, while the lactate and acetate concentrations were 0.2 mM (0.009 g/L) and 2.9 mM (0.13 g/L) correspondingly. An increase in the substrate loadings to 250 g/L in a batch fermenter (3 L) resulted in the production of 373.35 mM (17.1 g/L) of ethanol concentration and Yp/s of 0.16 g/g of reducing sugar.