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Whey is a by-product of paneer, cheese and casein industry and considered as a dairy waste. Worldwide, approximately 180–1,900 million tons of whey is produced annually. Whey is classified as a high pollutant due to its organic matter level. Owing to its high chemical oxygen demand and biological oxygen demand, it is a big threat to the environment. Whey contains 4.5%–5.0% lactose, 0.6%–0.7% protein, 0.4%–0.5% lipids, vitamins and minerals. Due to its high nutritional profile, it is a good substrate for the microorganisms for production of natural pigments. The purpose of this paper is to review the utilization of low cost substrate (whey) for production of various types of pigments and their applications in different sectors.

The databases for the search included: Scopus, PubMed, Science Direct, Web of Science, Research gate and Google. The main search was directed towards different types of natural pigments, stability, technologies for enhancing their production and contribution towards circular economy. Approximately 100 research papers were initially screened. A global search was conducted about natural pigments. Research articles, review papers, books, articles in press and book chapters were the type of search for writing this review paper.

Production of natural pigments using whey and their addition in food products not only improves the colour of food but also enhances the antioxidant properties of food products, helping the health benefits by chelating free radicals from the body. The sustainable use of whey for production of natural pigments can improve the bio-based economy of different industries and thereof the national economy.

Efficient utilization of whey can bring a lot more opportunities for production of natural pigments in a sustainable manner. The sustainable approach and circular economy concepts will benefit the dependent industries and health conscious consumers. The potential uses of whey for the production of natural pigments using diverse organisms are highlighted in this paper.

The purpose of this study is to isolate yellow pigment producing fungal strain and to determine the media requirement for growth and secondary metabolite production.

Fifteen soil samples were collected and studied for a pigment producing fungal sources. Selection of a fungus was based on pigment produced and further conditions, such as effect of media composition and light wavelength on pigment production and growth parameters were optimised.

Out of the isolates analysed, Epicoccum nigrum was selected for further study as this strain has the potential for pigment production. Among all the media evaluated, potato dextrose agar (PDA) was found to be the best media for growth and sporulation, whilst sabouraud dextrose agar (SDA) was only 29 per cent as capable as the best medium. The radial growth rate in case of PDA was 3 ± 0.02 mm/day, while in case of SDA, it was only 1.09 mm/day. Whilst starch as a carbon source was found to increase the radial growth to 5.15 ± 0.02 mm/day, sucrose significantly (p < 0.05) influenced the sporulation (224,000 ± 1,550 spores/ml) of Epicoccum nigrum. Amongst the various nitrogen sources analysed, peptone significantly increased (p < 0.05) the radial growth (6.55 ± 0.02 mm/day) as well as sporulation (220,000 ± 2,100 spores/ml). The observations also indicated that E. nigrum is able to sense and differentiate between light in different wavelength ranges and respond differently in growth and sporulation. The light passing through a red colour sheet resulted in better radial growth (8.5 ± 0.02 mm/day) in comparison to unfiltered light (3 ± 0.02 mm/day). Yellow pigment production in terms of hue values was significantly influenced by the presence of dextrose, peptone and darkness.

The isolated strain could be studied for variable conditions and stress factors for optimal production of the pigment. Recovery and purification studies could be carried out at pilot and industrial scale.

The isolation of a strain producing valuable microbial pigment will increase the alternatives of natural food colours and enhance the its commercial applications

This study identifies Epicoccum nigrum as a potential source of microbial pigment and facilitates its growth and production for possible applications in industrial pigment production.

This paper aims to isolate fungal strains producing natural colours, explore their application as colourant in paints and develop cost-effective durable natural paints.

Fungal strains producing natural colours of different shades were isolated. Colourant production was carried out by fermentation method. Natural lime, milk, oil-in-water emulsion paints using natural microbial colours and eco-friendly ingredients were prepared. Bio-paint applications were carried out and evaluated.

Our results indicate that microbes in general and fungi in specific represent dependable source of variety of natural colours, and cost-effective durable natural paints can be prepared with commonly available natural ingredients using scientific information based on history of paints.

Natural colours are gaining importance because of their use in health, nutrition, pharmaceutical, textile and environmental applications. Nature is quite rich in several types of colourants. Chemical synthesis of synthetic dyes is complex and not environmental friendly. Microbial dyes manufactured can evade inherent environmental problems of synthetic dyes and offer significant opportunity as a colourant in paints. However, only generally regarded as safe microbial strains are to be considered for colour production.

Choosing natural alternatives to protect the health and environment is the need of hour. Fungal colourants are relatively more stable and robust and offer significant opportunity as a colourant in paints. Cost-effective durable natural paints can be prepared using selected stable fungal colourants with commonly available natural ingredients. High diversity of rich and complex natural colourants can be obtained from microorganisms. With the available techniques of fermentation, natural colours can be produced in large quantities of on an economically viable scale and explored for their applications.

Bio-paints are eco-friendly natural paints, low volatile organic compounds (VOC) paints or organic paints alternate to conventional paints. Most of these natural paints are durable, breathable, prevent moisture problems, contribute to a positive room climate, use safer technology and are less energy-intensive than conventional latex paints to produce. These paints improve indoor air quality and reduce urban smog and offer beneficial characteristics such as low odour, excellent durability and a washable finish.

Many of the old art works that still survive today are a tangible proof and evidence of beauty and durability of natural paints. Organic materials used in these paints include natural pigments of mineral, plant and animal origin and other raw biodegradable ingredients. Successful commercialisation of many microbial pigments for food and textile applications is reported in literature. Therefore, present research work aims at developing natural paints using microbial pigments and recipes that have been successfully used by people for years.

The extraction of bioactive compounds such as pigments from natural sources, using different solvents, is a vital downstream process. The present study aims to investigate the effect of different variables, namely, extraction temperature, mass of fermented rice and time on the extraction process of orevactaene and flavanoid pigment from Epicoccum nigrum fermented broken rice.

Central composite rotatable design under response surface methodology was used for deducing optimized conditions. The pigments were extracted under conditions of extraction temperature (40-70°C), mass of fermented rice (0.5-1.5 g) and time (30-90 min), using water as the extraction media. The experimental data obtained were studied by analysis of variance. Data were fitted to a second-order polynomial equation using multiple regression analysis.

The optimum conditions generated by the software for aqueous extraction process, i.e. extraction temperature of 55.7°C, 0.79 g of fermented matter and extraction time of 56.6 min, resulted in a pigment yield of 52.7AU/g orevactaene and 77.2 AU/g flavanoid.

The developed polynomial empirical model for the optimal recovery of the orevactaene and flavanoid pigments could be used for further studies in prediction of yield under specified variable conditions.

The response surface methodology helped in optimizng the conditions for the eco-friendly low-cost aqueous extarction process for orevactaene and flavanoid pigments, produced by Epicoccum nigrum during solid state fermentation of broken rice. This optimization can provide the basis for scaling up for industrial extraction process.

This paper focuses on optimizing the extraction conditions to get the maximum yield of orevactaene and flavanoid pigments, using water as the extracting media. No literature is available on the optimization of the extraction process of Epicoccum nigrum pigments, to the best of the authors’ knowledge.

A major challenge facing the fresh‐cut industry is maintaining and preserving the quality of minimally processed or fresh‐cut produce. A low temperature regime, although insufficient, has been the main method of overcoming this challenge so far. Thus, methods preserving the quality and extending the shell life of minimally processed or fresh‐cut produce are needed. This paper seeks to propose that honey could be used to preserve the fresh‐like quality of minimally processed pomegranate arils and extend their shelf life.

Manually extracted pomegranate arils were treated with water as control, 10 or 20 per cent diluted honey solution each for five minutes, then held at 4°C for ten days. Changes in organoleptic and visual quality, softening, soluble solids content, pH, absorbance at 446 and 510nm, and total aerobic count were recorded during the ten‐day storage period.

The study found that honey solution dip treatments extended the fresh‐like quality of minimally processed arils by delaying quality loss, microbial development, and pigment changes.

The paper shows that honey dip treatment may be used, depending on commodity, to preserve quality and extend the shelf life of minimally processed or fresh‐cut produce in the food‐processing industry.

The study pays particular attention to minimally processed pomegranate arils, by adapting a potentially safe organic method, the use of honey dips.

Carotenoids are pigments that have significant value as colorants and antioxidants in pharmaceutical, food, textile and cosmetic industries. Owing to its high demand, this study aims to identify ß-carotene producing bacteria from different terrestrial habitats of Jaipur region.

In this paper, standard isolation and purification process was used, followed by colony morphology and biochemical characterization of ß-carotene producing bacteria. ß-carotene concentration was determined quantitatively using spectrophotometric method.

Out of 43 isolates, 21 isolates showed peak range between 400 and 500 nm confirming the presence of carotenoids. Only one bacteria SAN-A has capacity to produce ß-carotene confirmed by the thin layer chromatography and high performance liquid chromatography (HPLC) with a yield of 1.68 mg/l. The 2, 2-Diphenyl-2-picrylhydrazil (DPPH) assay showed an IC50 value of 4.0 mg/ml.

The present study revealed the presence of ß-carotene producing bacteria in the soil of different terrestrial habitat of Jaipur region which can be exploited as an economical source for ß-carotene production.

Biopigments, natural colors from microbiological origin are of great interest because of their potential advantages over synthetic colorants. Therefore, this paper aims to evaluate the best possible fermentative conditions for the maximum production of biopigment using solid state fermentation and submerged fermentation by Monascus purpureus MTCC 369.

The biopigment was produced using solid state fermentation and submerged with optimized substrate to achieve higher yield. The statistical analysis was carried out using a Microsoft Excel ® (Microsoft Corporation).

On comparative analysis, it was observed that solid state fermentation resulted significant accumulation of biopigment (9.0 CVU/g) on the 9th day in comparison to submerged fermentation (5.1 CVU/g) on the 15th day.

Results revealed that sweet potato peel powder and pea pods provides necessary nutrients required for mycelial growth, and biopigment production, therefore, can be used as potent substrate for biopigment production by Monascus purpureus MTCC 369. Extracted color can be used in confectionery, beverages and pharmaceutical industries.

This work focuses on utilisation of waste for production of pigment as alternative source to synthetic colorant, and few studies have been carried out using wastes, but no work has been carried out on sweet potato peel to the best of the authors’ knowledge.

The purpose of this paper was to identify Serratia marcescens to extract and purify prodigiosin pigment to evaluate the antibacterial potential of the pigment.

Samples were collected from shrimp aquaculture ponds. Species identification was conducted using morphological, biochemical and molecular tests. Pigment extraction and purification were carried out using column chromatography. The antibacterial effect of crude and purified prodigiosin pigment was evaluated on Escherichia coli, Bacillus subtilis, Pseudomonas aeruginosa and Staphylococcus aureus as biofouling bacteria. In addition, the interaction between prodigiosin and proteins involved in biofilm formation was evaluated using molecular docking.

The results of prodigiosin extraction with solvents showed the highest percentage of pigment presence with methanol solvent in the second day of culture. The chemical structure of pure prodigiosin obtained from the column chromatography was confirmed by Fourier-transform infrared spectroscopy. Both crude and purified pigments exhibited antibacterial effects against selected bacterial strains. The antibacterial effect of the purified pigment was higher, and the highest antibacterial effect was observed on B. subtilis. Prodigiosin docking was carried out with all target proteins, and the docked energy in all of them was at an acceptable level.

Prodigiosin extracted from S. marcescens can be used as a bioactive compound to design and manufacture of anti-biofouling and anti-biofilm formation products to use extensively for industrial applications as a natural color in marine industries, food industry, cosmetics and textile productions.

Modern thermal and non-thermal pretreatment techniques, namely, enzymatic treatment, gas phase plasma treatment and ohmic heating have become more pronounced over conventional techniques for enhanced coloured phytochemicals (pigments) extraction. Presently, numbers of pretreatment techniques are available with some unique feature. It is difficult to choose best pretreatment method to be employed for phytochemicals extraction from different sources. Therefore, this paper aims to discuss different modern pretreatment techniques for extraction with their potential results over conventional techniques.

Research and review articles targeting to the thermal and non-thermal pretreatment techniques were collected from Google Scholar. The required information has been tabulated and discussed which included qualities of modern pretreatment techniques over conventional techniques, phytochemical extraction and best pretreatment methods for optimized results.

Every pre-treatment has its own advantages and disadvantages for a particular phytochemical and its extraction from various sources. Enzymes can be used in combinations to enhance final yield like extraction of carotenoids (pectinase, cellulase and hemicellulase) from chillies and lycopene (pectinase and cellulase) from tomato. Utilization of each method depends upon many factors such as source of pigment, cost and energy consumption. CO₂ pretreatment gives good results for carotenoid extraction from algae sources. Ohmic heating can yield high anthocyanin content. Modifications in conventional blanching has reduced final waste and improvised the properties of pigment.

This study comprises collective information regarding modern pre-treatment for extraction over conventional pre-treatments. The study also covers future trends and certain new hybrid approaches which are still less flourished.

The purpose of this study is to address consumer’s preference of natural pigments over synthetic ones and their use in various product developments rather than using synthetic colours. A budding interest of using natural pigments has made researchers to explore several techniques for their stabilization and application in different food products.

In this review, four major natural pigments with potential health benefits have been studied. Betalins, carotenoids, anthocyanins and chlorophylls, in spite of having excellent bio-functional and therapeutic profile, are found to be unstable. Therefore, various nanoencapsulation techniques are used to increase their stability along with their therapeutic properties.

Nanoencapsulation of natural pigments improves their stability, their effect on therapeutic properties and their application in different food products. These findings could be attributed to the encapsulating material as it acts as a barrier and ushers changes in the matrix of natural pigments. Also, nanoencapsulation not only increases stability but also provides several health benefits such as anti-inflammation, anti-cancer, anti-allergic and anti-thrombotic properties.

This paper highlights the openings for the use of nanoencapsulation of natural pigments to stabilize them and use them as a potential colourant and functional ingredient in different food products. Phenols, carotenoids and antioxidant activity are the major factors that are responsible for promoting several health benefits.