Carbohydrate structures as part of the melanoidin skeleton

Extracted dyes' stability as obtained from spent coffee grounds on silk fabrics using eco-friendly mordants

Spent coffee grounds (SCGs) are commonly known as a waste resource and a raw material useful for dyeing. SCG is a rich source of natural colorant from the class of flavonoids and anthocyanins. In this research, silk fiber dyeing with the dye which was extracted from SCGs with different metallic and natural mordants was done by applying pre-, meta-, and post-mordanting methods. Metal salts like tin chloride and copper sulfate as well as such natural materials as pinecone, tannic acid, and lemon peel were used to act as mordants. Color strength and color parameters of the dyed silk fabric samples were evaluated by applying a reflective spectrophotometer. Also, the evaluation of wash and light fastness was done based on ISO standards. The results indicated that in all methods, the metal samples had higher color strength when compared to the bio-mordant ones. Among the used methods and bio-mordants, the use of the pre-mordanting method and pinecone led to the highest amount of color strength. Also, the used bio-mordant could be a suitable substitute for metal mordants in terms of fastness parameters. Among the used methods and mordants, the post-mordanting method and pinecone mordant could provide the best washing and light fastness.

Bioactive compounds as an alternative for the sugarcane industry: Towards an integrative approach

Here, a comprehensive review of sugarcane industrialization and its relationship with bioactive compounds (BCs) detected in various products and by-products generated during its processing is presented. Furthermore, it is discussed how these compounds have revealed important antioxidant, antineoplastic, antidiabetic, and antimicrobial activities. From this bibliographic research highlights the significance of two types of BCs of natural origin (phenolic compounds (PCs) and terpenoids) and a group of compounds synthesized during industrial transformation processes (Maillard reaction products (MRPs)). It was found that most of the studies about the BCs from sugarcane have been conducted by identifying, isolating, and analyzing ones or a few compounds at a specific period, this being a conventional approach. However, given the complexity of the synthesis processes of all these BCs and the biological activities they can manifest in a specific biological context, novel approaches are needed to address these analyses holistically. To overcome this challenge, integrating massive and multiscale methods, such as omics sciences, seems necessary to enrich these studies. This work is intended to contribute to the state of the art that could support future research about the exploration, characterization, or evaluation of different bioactive molecules from sugarcane and its derivatives.

Kinetics of L-ascorbic acid degradation and non-enzymatic browning development in hot-compressed water

The effect of reaction conditions, which comprised the reaction temperature (150-190°C), processing time (0.50, 0.75, 1.00, 1.25, 1.50, 2.00, and 2.50 h), pH (5.0, 7.0, and 9.5), and concentration (0.03-0.07 mol/L) of L-ascorbic acid (ASA), on the degradation of ASA was investigated in hot-compressed water (HCW). The degradation kinetics of ASA and generation kinetics of browning products (BPs) were studied. The results showed that ASA degradation conformed to the pseudo-first-order kinetics, and the formation of BPs was closely related to the concentration of H₃O⁺ in HCW. The acidic condition (pH = 5.0) and lower concentration of ASA (0.03 mol/L) were more favorable for ASA degradation. In HCW, the average apparent activation energy (Ea) of ASA was 15.77, 31.70, and 47.53 kJ/mol at pH 5.0, 7.0, and 9.5, respectively. The possible degradation mechanisms of ASA and the generation of BPs in HCW were proposed based on the experimental results.

Effects of sludge thermal hydrolysis pretreatment on anaerobic digestion and downstream processes: mechanism, challenges and solutions

Thermal hydrolysis pretreatment (THP), as a step prior to sludge anaerobic digestion (AD), is widely applied due to its effectiveness in enhancing organic solids hydrolysis and subsequent biogas productivity. However, THP also induces a series of problems including formation of refractory compounds in THP cylinder, high residual ammonia and organic in the AD centrate, inhibition on downstream nitrogen removal process and reduction in UV-disinfection effectiveness during post-treatment. More attention should be paid on how to mitigate these negative effects. Despite intensive studies were carried out to reduce refractory compounds formation and enhance biological performance, there is limited effort to discuss the solutions to tackle the THP associated problems in a holistic manner. This paper summarizes the solutions developed to date and analyzes their technology readiness to assess application potential in full-scale settings. The content highlights the limitations of THP and proposes potential solutions to address the technological challenges.

Valorization of Distillery Stillage for Bioenergy Production: A Review

In alcohol distilleries, the amount of distillery stillage generated can be up to 15 times larger than the amount of alcohol produced. The stillage has high concentrations of organics and nitrogen, a low pH, and a dark brown color. Currently, stillage is mainly used for soil fertilization. For this purpose, it requires thickening and is used seasonally, which creates storage problems and transport costs. To reduce environmental pollution, physicochemical and biological processes have been employed for the treatment of distillery stillage. However, according to bioeconomy principles, the stillage should be transformed into value-added products. Therefore, this review paper focuses on methods of stillage processing that enable energy recovery. Due to its high content of organic compounds, stillage is often used as a raw material for biogas production. Accordingly, anaerobic digestion of stillage is discussed, including an overview of the bioreactors used and the effects of operational parameters on organics removal and biogas production. The necessity of integrating anaerobic stillage treatment with other treatment processes is presented. As complex compounds that are present in the stillage (mainly polyphenols and melanoidin) are difficult to biodegrade and have antibacterial activities, the effect of their recovery on biogas production is described. Next, the possibility of converting distillery stillage to bioethanol and biohydrogen is presented. In addition, bioelectrochemical treatment of distillery stillage using microbial fuel cells is discussed. For all these treatment methods, current challenges and opportunities are given.

Current trends and advances in analytical techniques for the characterization and quantification of biologically recalcitrant organic species in sludge and wastewater: A review

The study of organic matter in wastewater is a major regulatory and environmental issue and requires new developments to identify non-biodegradable refractory compounds, produced mainly by thermal treatments. Recent advances linking physicochemical properties to spectroscopic analyzes (UV, Fluorescence, IR) have shown that the refractory property is favored by several physicochemical parameters: weight, hydrophobicity, aromaticity and chemical functions. Currently, the most effective developments for the quantification of refractory compounds are obtained with hyphenated methods, based on steric separation of the macromolecular species by steric exclusion chromatography (SEC)/PDA/Fluorescence systems. Hyphenated techniques using High Resolution Mass Spectrometry (HRMS), ultra-high-resolution mass spectrometry with Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS) and NMR have been developed to analyze macromolecules in wastewater with minor sample preparation procedures. A particular class has been identified, the melanoidins, generated by Maillard reactions between sugars, amino acids, peptides and proteins present in wastewater and sludge, but low molecular weight compounds formed as intermediates, such as ketones, aldehydes, pyrazines, pyridines or furans, are also recalcitrant and are complex to identify in the complex matrices. The lack of available standards for the study of these compounds requires the use of specific techniques and data processing. Advances in chemometrics are obtained in the development of molecular or physicochemical indices resulting from the data generated by the analytical detectors, such as aromaticity calculated by SUVA₂₅₄ and determined by UV, fluorescence, molar mass, H/C ratio or structural studies (measuring the amount of unsaturated carbon) given by hyphenated techniques with SEC. It is clear that nitrogen compounds are widely involved in refractoriness. New trends in nitrogen containing compounds characterization follow two axes: through SEC/PDA/Fluorescence and HRMS/NMR techniques with or without separation. Other techniques widely used in food or marine science are also being imported to this study, as it can be seen in the use of "omics" methods, high-performance thin layer chromatography (HPTLC) and chromatography at the critical condition, rounding out the important developments around SEC. While improving the performance of stationary phases is one of the challenges, it results in a fundamental understanding of the retention mechanisms that today provide us with more information on the structures identified. The main objective of this review is to present the spectroscopic and physicochemical techniques used to qualify and characterize refractoriness with a specific focus on chemometric approaches.

Environmental pollution and health hazards from distillery wastewater and treatment approaches to combat the environmental threats: A review

Distillery industries are the key contributor to the world's economy, but these are also one of the major sources of environmental pollution due to the discharge of a huge volume of dark colored wastewater. This dark colored wastewater contains very high biological oxygen demand, chemical oxygen demand, total solids, sulfate, phosphate, phenolics and various toxic metals. Distillery wastewater also contains a mixture of organic and inorganic pollutants such as melanoidins, di-n-octyl phthalate, di-butyl phthalate, benzenepropanoic acid and 2-hydroxysocaproic acid and toxic metals, which are well reported as genotoxic, carcinogenic, mutagenic and endocrine disrupting in nature. In aquatic resources, it causes serious environmental problems by reducing the penetration power of sunlight, photosynthetic activities and dissolved oxygen content. On other hand, in agricultural land, it causes inhibition of seed germination and depletion of vegetation by reducing the soil alkalinity and manganese availability, if discharged without adequate treatment. Thus, this review article provides a comprehensive knowledge on the distillery wastewater pollutants, various techniques used for their analysis as well as its toxicological effects on environments, human and animal health. In addition, various physico-chemicals, biological as well as emerging treatment methods have been also discussed for the protection of environment, human and animal health.

Concentrating molasses distillery wastewater using biomimetic forward osmosis (FO) membranes

Treatment of sugarcane molasses distillery wastewater is challenging due to the presence of complex phenolic compounds (melanoidins and polyphenols) having antioxidant properties. Due to zero liquid discharge regulations, Indian distilleries continue to explore effective treatment options. This work examines the concentration of distillery wastewater by forward osmosis (FO) using aquaporin biomimetic membranes and magnesium chloride hexahydrate (MgCl₂.6H₂O) as draw solution. The operational parameters viz. feed solution and draw solution flow rate and draw solution concentration were optimized using 10% v/v melanoidins model feed solution. This was followed by trials with distillery wastewater. Under the conditions of this work, feed and draw flow rates of 1 L/min and draw solution concentration of 2M MgCl₂.6H₂O for melanoidins model solution and 3M MgCl₂.6H₂O for distillery wastewater were optimal for maximum rejection. Rejection of 90% melanoidins, 96% antioxidant activity and 84% COD was obtained with melanoidins model feed, with a corresponding water flux of 6.3 L/m²h. With as-received distillery wastewater, the rejection was similar (85-90%) to the melanoidins solution, but the water flux was lower (2.8 L/m²h). Water recovery from distillery wastewater over 24 h study period was higher with FO (70%) than reported for RO (35-45%). Repeated use of the FO membrane over five consecutive 24 h cycles with fresh feed and draw solutions and periodic cleaning showed consistent average water flux and rejection of the feed constituents.

Decolourization of melanoidins by a electrocoagulation process using aluminium electrodes

The decolourization ofmelanoidins was studied with a batch electrocoagulation (EC) process using aluminium electrodes. The effects of conductivity (K = 500-3000 microS/cm), initial pHi (4.2-8.2), current density (j = 2.5-7.5 A/m2), initial melanoidin concentration (C0 = 100-800 mg/L) and operating time (tEC = 0-60 min) were investigated on the decolourization efficiency. The results obtained from the EC process were extremely efficient and able to achieve a decolourization efficiency of > 98% at pHi = 4.2, j = 5 A/m2, K = 2500 microS/cm, C0 = 100 mg/L and tEC = 10 min. The decolourization performance was dependent on pHi value since the lower pH values led to faster reactions and higher decolourization efficiency. Melanoidins in the EC process were removed by precipitation and charge neutralization at pH < 6.5, and both adsorption and sweep coagulation by amorphous Al(OH)3(s) occurred at pH > 6.5. The operating cost was calculated as 0.0096 Euro/m3

Effect of thermal pretreatment on the physical and chemical properties of municipal biomass waste

The effects of thermal pretreatment on the physical and chemical properties of three typical municipal biomass wastes (MBWs), kitchen waste (KW), vegetable/fruit residue (VFR), and waste activated sludge (WAS) were investigated. The results show that thermal pretreatment at 175 °C/60 min significantly decreases viscosity, improves the MBW dewatering performance, as well as increases soluble chemical oxygen demand, soluble sugar, soluble protein, and especially organic compounds with molecular weights >10 kDa. For KW, VFR and WAS, 59.7%, 58.5% and 25.2% of the organic compounds can be separated in the liquid phase after thermal treatment. WAS achieves a 34.8% methane potential increase and a doubled methane production rate after thermal pretreatment. In contrast, KW and VFR show 7.9% and 11.7% methane decrease because of melanoidin production.

High molecular weight coffee melanoidins are inhibitors for matrix metalloproteases

High molecular (above 10 kDa) melanoidins isolated from coffee beans of varying roasting degree were found to be efficient inhibitors for the zinc-containing matrix metalloproteases MMP-1, MMP-2, and MMP-9 with IC(50) values ranging between 0.2 and 1.1 mg/mL in vitro. The inhibitory potential increased with roasting degree. No or only slight inhibition of other zinc-containing peptidases closely related to MMPs, namely, Clostridium histolyticum collagenase and angiotensin converting enzyme, was found, indicating specific structural features of melanoidins to be responsible for the interaction with MMPs. A continuous increase on the apparent molecular weight of melanoidins as well as incorporation of phenolic substances into the melanoidin structure with progress of roasting was observed, concomitant with a significant increase in the carbon/nitrogen of the melanoidins. This suggests that the melanoidins are mainly formed by incorporation of carbohydrates and phenolic compounds onto a proteinaceous backbone. As MMP-1, MMP-2, and MMP-9 play a pivotal role in pathogenesis of colorectal cancer, studies on possible physiological effects of melanoidins are mandatory.

Melanoidins as major colourant in sugarcane molasses based distillery effluent and its degradation

Melanoidins are natural condensation products of sugar and amino acids produced by non-enzymatic Maillard amino-carbonyl reaction taking place between the amino and carbonyl groups in organic substances. Melanoidins extensively exist in food products, drinks and wastewaters released from distilleries and fermentation industries. Melanoidins are very important from the nutritional, physiological and environmental aspects and due to their structural complexity, dark colour and offensive odor, these pose serious threat to soil and aquatic ecosystem that release of melanoidins cause increased load of recalcitrant organic material to natural water bodies. This then causes the problems, like reduction of sunlight penetration, decreased photosynthetic activity and dissolved oxygen concentration whereas on land, it causes reduction in soil alkalinity and inhibition of seed germination. Further, due to the possibility of complexation reactions of introduced melanoidins with metal ions, they could influence the biogeochemical cycle of many constituents in natural waters. This review presents an overview to dramatic progress to understand the synthesis, chemical structure and degradation pathway of melanoidins as well as microbial strategies for the degradation and decolourisation of melanoidins.

Biological decolourisation of wastewater from molasses fermentation by Trametes versicolor in an airlift reactor

Continuous decolourisation of wastewater from molasses fermentation using mycelium of Trametes versicolor in pellets shape was performed in an airlift bioreactor (semi-pilot scale) with the aim of operating steadily for a long period, maintaining the colour removal activity. The influences of influent flow and glucose feed rate were tested. Induction of peroxidases secretion by Mn(2+) addition was also studied. The efficiency of the decolourisation process was followed by monitoring colour and enzymatic activities. The experimental results showed that continuous decolourisation in an airlift bioreactor can be considered a suitable alternative for treating molasses fermentation wastewater. A colour removal yield around 60% remained practically constant during 23 days under continuous operation. Laccase was found to be the main enzyme secreted by the strain, being responsible for the decolourisation process. Mn(2+) addition was not likely to induct manganese-dependent peroxidase secretion.

Microbial decolorization of spentwash: a review

Spentwash is one of the most complex and cumbersome wastewater with very high BOD, COD and other organic and inorganic toxic constituents. It is dark brown colored and difficult to treat by normal biological process such as activated sludge or anaerobic lagooning. The color is due to the presence of melanoidins, caramels and other polymers. These compounds have anti oxidant properties which render them toxic to microorganisms. Spentwash disposal into the environment is hazardous and has a considerable pollution potential. It affects the aesthetic merit. Its decolorization by physical or chemical methods have been investigated and were found unsuitable. In the recent past, increasing attention has been directed towards utilizing microbial activity for decolorization of spentwash. This review reveals various groups of microorganisms which have potential in spentwash decolorization. The role of enzymes in decolorization and the microbial degradation of individual compounds imparting color to spentwash are also discussed.

Biological approaches for treatment of distillery wastewater: a review

Effluent originating from distilleries known as spent wash leads to extensive soil and water pollution. Elimination of pollutants and colour from distillery effluent is becoming increasingly important from environmental and aesthetic point of view. Stillage, fermenter and condenser cooling water and fermenter wastewater are the primary polluting streams of a typical distillery. Due to the large volumes of effluent and presence of certain recalcitrant compounds, the treatment of this stream is rather challenging by conventional methods. Therefore, to supplement the existing treatments, a number of studies encompassing physico-chemical and biological treatments have been conducted. This review presents an account of the problem and the description of colour causing components in distillery wastewater and a detailed review of existing biological approaches. Further, the studies dealing with pure cultures such as bacterial, fungal, algal and plant based systems have also been incorporated. Also, the roles of microbial enzymes in the decolourization process have been discussed to develop a better understanding of the phenomenon.

Continuous ozonation of biologically pretreated molasses fermentation effluents

In this work, continuous chemical oxidation processes (single ozonation and ozone combined with hydrogen peroxide) of biologically pretreated wastewaters from a beet molasses fermentation factory have been studied. Oxidation processes were carried out in a stirred tank reactor at the natural pH of the wastewater and 25 degrees C, analyzing the effect of the hydraulic residence time and applied ozone mass flow on color and organic matter removals. Ozone consumption was also measured in each experiment. The results show that continuous ozonation was effective for decolorization of molasses wastewater. Operating with a hydraulic residence time of 45 minutes and an applied ozone mass flow of 1.7 g/h, color and chemical oxygen demand (COD) reductions were about 80% and 14%, respectively. Increasing the hydraulic residence time or ozone mass flow led to a considerably increase in the ozone consumption, with similar color and organic matter reduction percentages. Slightly higher removal percentages were obtained combining ozone with hydrogen peroxide, attaining 83% color reduction and 20% COD removal. As consequence of the oxidation processes, biodegradability of the decolorized effluent increased about 40-50% and the ratio BOD5/COD was twofold higher.