Utilization of Agro-Industry Residue for Rhamnolipid Production by P. aeruginosa AMB AS7 and Its Application in Chromium Removal

Glycolipids biosurfactants production using low-cost substrates for environmental remediation: progress, challenges, and future prospects

The production of renewable materials from alternative sources is becoming increasingly important to reduce the detrimental environmental effects of their non-renewable counterparts and natural resources, while making them more economical and sustainable. Chemical surfactants, which are highly toxic and non-biodegradable, are used in a wide range of industrial and environmental applications harming humans, animals, plants, and other entities. Chemical surfactants can be substituted with biosurfactants (BS), which are produced by microorganisms like bacteria, fungi, and yeast. They have excellent emulsifying, foaming, and dispersing properties, as well as excellent biodegradability, lower toxicity, and the ability to remain stable under severe conditions, making them useful for a variety of industrial and environmental applications. Despite these advantages, BS derived from conventional resources and precursors (such as edible oils and carbohydrates) are expensive, limiting large-scale production of BS. In addition, the use of unconventional substrates such as agro-industrial wastes lowers the BS productivity and drives up production costs. However, overcoming the barriers to commercial-scale production is critical to the widespread adoption of these products. Overcoming these challenges would not only promote the use of environmentally friendly surfactants but also contribute to sustainable waste management and reduce dependence on non-renewable resources. This study explores the efficient use of wastes and other low-cost substrates to produce glycolipids BS, identifies efficient substrates for commercial production, and recommends strategies to improve productivity and use BS in environmental remediation.

Production and characterization of extracellular liamocins produced from fungal strains of Aureobasidium spp

Liamocins, a group of high-density glycolipids, are only produced by certain strains of the yeast-like fungi in the genus Aureobasidium. Until now, few studies have focused on the surfactant properties of liamocins produced from the highly diverse tropical strains of Aureobasidium. Therefore, the aims of this research were to screen the liamocin production from tropical strains of Aureobasidium spp. and to characterize their surfactant properties. A total of 41 strains of Thai Aureobasidium spp. were screened for their ability to produce liamocins, and the products were detected using matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and thin-layer chromatography. Of those strains, 30 strains of Aureobasidium spp. tested were found to produce liamocins with yields ranging from 0.53 to 10.60 g/l. The nature of all crude liamocins was heterogeneous, with different compositions and ratios depending on the yeast strain. These liamocins exhibited relatively high emulsifying activity against vegetable oils tested, with an emulsification index of around 40-50%; the emulsion stability of some liamocins was up to 30 days. The obtained critical micelle concentration values were varied, with those ​​of liamocins produced from A. pullulans, A. melanogenum and A. thailandense falling in ranges from 7.70 to 119.78, 10.73 to > 1,000, and 68.56 to > 1,000 mg/l, respectively. The emulsification activity of liamocins was higher than that of the analytical grade rhamnolipids. These compounds showed strong surface tension reduction in a sodium chloride concentration range of 2-12% (w/v), pH values between 3 and 7, and temperatures between 4 and 121 °C. This is the first report of liamocins produced by A. thailandense.

Unlocking the potential of biosurfactants: Production, applications, market challenges, and opportunities for agro-industrial waste valorization

Biosurfactants are eco-friendly compounds with unique properties and promising potential as sustainable alternatives to chemical surfactants. The current review explores the multifaceted nature of biosurfactant production and applications, highlighting key fermentative parameters and microorganisms able to convert carbon-containing sources into biosurfactants. A spotlight is given on biosurfactants' obstacles in the global market, focusing on production costs and the challenges of large-scale synthesis. Innovative approaches to valorizing agro-industrial waste were discussed, documenting the utilization of lignocellulosic waste, food waste, oily waste, and agro-industrial wastewater in the segment. This strategy strongly contributes to large-scale, cost-effective, and environmentally friendly biosurfactant production, while the recent advances in waste valorization pave the way for a sustainable society.

High mono-rhamnolipids production by a novel isolate Pseudomonas aeruginosa LP20 from oily sludge: characterization, optimization, and potential application

This study aims to isolate microbial strains for producing mono-rhamnolipids with high proportion. Oily sludge is rich in petroleum and contains diverse biosurfactant-producing strains. A biosurfactant-producing strain LP20 was isolated from oily sludge, identified as Pseudomonas aeruginosa based on phylogenetic analysis of 16S rRNA. High-performance liquid chromatography-mass spectrometry results indicated that biosurfactants produced from LP20 were rhamnolipids, mainly containing Rha-C8-C10, Rha-C10-C10, Rha-Rha-C8-C10, Rha-Rha-C10-C10, Rha-C10-C12:1, and Rha-C10-C12. Interestingly, more mono-rhamnolipids were produced by strain LP20 with a relative abundance of 64.5%. Pseudomonas aeruginosa LP20 optimally produced rhamnolipids at a pH of 7.0 and a salinity of 0.1% using glycerol and nitrate. The culture medium for rhamnolipids by strain LP20 was optimized by response surface methodology. LP20 produced rhamnolipids up to 6.9 g L-1, increased by 116%. Rhamnolipids produced from LP20 decreased the water surface tension to 28.1 mN m-1 with a critical micelle concentration of 60 mg L-1. The produced rhamnolipids emulsified many hydrocarbons with EI24 values higher than 56% and showed antimicrobial activity against Staphylococcus aureus and Cladosporium sp. with inhibition rates 48.5% and 17.9%, respectively. Pseudomonas aeruginosa LP20 produced more proportion of mono-rhamnolipids, and the LP20 rhamnolipids exhibited favorable activities and promising potential in microbial-enhanced oil recovery, bioremediation, and agricultural biocontrol.

Response of aerobic activated sludge to edible oil exposure: Extracellular polymeric substance (EPS) characteristics and microbial community

Aerobic activated sludge is widely used to degrade edible oil wastewater in wastewater treatment plants. During this process, the observed poor organics removal performance might be caused by poor sludge settling performance, which might be influenced by extracellular polymeric substances (EPS) and the structure of the microbial community. However, this hypothesis was not confirmed. Thus, this study investigated the response of activated sludge to 50% and 100% edible oil exposure in comparison to glucose, focusing on organics removal performance, characteristics of sludge, EPS, and microbial community structure. Results showed that both concentrations of edible oil influenced the systems' performance, although 100% edible oil showed more significant negative effects than 50% edible oil. The mechanisms behind the influence of edible oil on the aerobic activated sludge system and the differences between the different concentrations of edible oil were revealed. The worse system performance in the edible oil exposure system was due to the worse sludge settling performance, which was significantly affected by edible oil (p < 0.05). The sludge settling performance was mainly inhibited by promoting the formation of floating particles and the enrichment of filamentous bacteria in the 50% edible oil exposure system; biosurfactant secretion was also speculated as the reason, in addition to the above factors, in the 100% edible oil exposure system. The macroscopic largest floating particles, highest total relative abundance of foaming bacteria and biosurfactant production genera (34.32%), lowest surface tension (43.7 mN/m), and highest emulsifying activity (E₂₄ = 25%) of EPS in 100% edible oil exposure systems provide strong evidence.

Sustainable production of biosurfactants via valorisation of industrial wastes as alternate feedstocks

Globally, the rapid increase in the human population has given rise to a variety of industries, which have produced a variety of wastes. Due to their detrimental effects on both human and environmental health, pollutants from industry have taken centre stage among the various types of waste produced. The amount of waste produced has therefore increased the demand for effective waste management. In order to create valuable chemicals for sustainable waste management, trash must be viewed as valuable addition. One of the most environmentally beneficial and sustainable choices is to use garbage to make biosurfactants. The utilization of waste in the production of biosurfactant provides lower processing costs, higher availability of feedstock and environmental friendly product along with its characteristics. The current review focuses on the use of industrial wastes in the creation of sustainable biosurfactants and discusses how biosurfactants are categorized. Waste generation in the fruit industry, agro-based industries, as well as sugar-industry and dairy-based industries is documented. Each waste and wastewater are listed along with its benefits and drawbacks. This review places a strong emphasis on waste management, which has important implications for the bioeconomy. It also offers the most recent scientific literature on industrial waste, including information on the role of renewable feedstock for the production of biosurfactants, as well as the difficulties and unmet research needs in this area.

Biosurfactant Production from Lactobacilli: an Insight on the Interpretation of Prevailing Assessment Methods

Biosurfactants constitute amphiphilic molecules, receiving increased attention as environmentally benign, biodegradable alternatives to substitute for the petroleum derived counterparts in food, pharmaceutical and cosmetics applications. However, their high production cost hinders industrial production. In this study, fifty GRAS lactobacilli strains were screened for their ability to produce biosurfactants, implementing different substrates. Cheese whey permeate (CWP) was also assessed as a low-cost and inherent lactobacilli substrate, aiming to mitigate its polluting impact, expand valorization strategies, alleviate costs deriving from commercial supplements and enhance overall sustainability. Surface tension, emulsification activity (E24) and oil displacement were deployed to identify the most promising candidates. Results reveal surface tension as the most robust method and underline the effect of substrate on biosurfactant synthesis. Likewise, this study indicates the fundamental role of including the final fermentation substrate (CWP) during strain selection to avoid misinterpretation of results and enhance subsequent bioprocess integration.

Characterization and Cytotoxicity of Pseudomonas Mediated Rhamnolipids Against Breast Cancer MDA-MB-231 Cell Line

A biosurfactant producing bacterium was identified as Pseudomonas aeruginosa DNM50 based on molecular characterization (NCBI accession no. MK351591). Structural characterization using MALDI-TOF revealed the presence of 12 different congeners of rhamnolipid such as Rha-C8-C8:1, Rha-C10-C8:1, Rha-C10-C10, Rha-C10-C12:1, Rha-C16:1, Rha-C16, Rha-C17:1, Rha-Rha-C10:1-C10:1, Rha-Rha-C10-C12, Rha-Rha-C10-C8, Rha-Rha-C10-C8:1, and Rha-Rha-C8-C8. The radical scavenging activity of rhamnolipid (DNM50RL) was determined by 2, 3-diphenyl-1-picrylhydrazyl (DPPH) assay which showed an IC₅₀ value of 101.8 μg/ ml. The cytotoxic activity was investigated against MDA-MB-231 breast cancer cell line by MTT (4,5-dimethylthiazol-2-yl-2,5-diphenyl tetrazolium bromide) assay which showed a very low IC50 of 0.05 μg/ ml at 72 h of treatment. Further, its activity was confirmed by resazurin and trypan blue assay with IC₅₀ values of 0.01 μg/ml and 0.64 μg/ ml at 72 h of treatment, respectively. Thus, the DNM50RL would play a vital role in the treatment of breast cancer targeting inhibition of p38MAPK.

Bioreactor Rhamnolipid Production Using Palm Oil Agricultural Refinery By-Products

Palm fatty acid distillate (PFAD) and fatty acid methyl ester (FAME) are used by P. aeruginosa PAO1 to produce rhamnolipid biosurfactant. The process of fermentation producing of biosurfactant was structured in a 2 L bioreactor using 2% of PFAD and FAME as carbon sources in minimal medium and with a nitrogen concentration of 1 g L−1. Mass spectrometry results show the crude biosurfactant produced was predominantly monorhamnolipid (Rha-C10-C10) and dirhamnolipid (Rha-Rha-C10-C10) at 503 and 649 m/z value for both substrates. Maximum production of crude rhamnolipid for PFAD was 1.06 g L−1 whereas for FAME it was 2.1 g L−1, with a reduction in surface tension of Tris-HCl pH 8.0 solution to 28 mN m−1 and a critical micelle concentration (CMC) of 26 mg L−1 measured for both products. Furthermore, the 24 h emulsification indexes in kerosene, hexadecane, sunflower oil, and rapeseed oil using 1 g L−1 of crude rhamnolipid were in the range 20–50%. Consequently, PFAD and FAME, by-products from the agricultural refining of palm oil, may result in a product that has a higher added-value, rhamnolipid biosurfactant, in the process of integrated biorefinery.

Rhamnolipids Application for the Removal of Vanadium from Contaminated Sediment

The use of biosurfactants in bioremediation of hydrocarbons and in the removal of heavy metals in crude oils is considered an attractive subject. The vanadium pollution in soil and sediments had attracted research interest in exploring eco-friendly methods of remediation. The present study was conducted to evaluate the potential of a biosurfactant to remove vanadium from artificially contaminated sand. The biosurfactant producer's strain selection process was carried out from 23 strains in two steps. In the primary screening, four preliminary tests were carried out: the emulsification index (24 and 72 h), the surface tension, and the rate of bacterial adhesion to hydrocarbons. In the secondary screening, the surface tension and rhamnolipids concentration were determined, also critical micellar concentration and dilution were calculated. The RNA 16s of selected strain was sequence and the strain was identified as Pseudomonas sp. By chromatographic and spectroscopic assays, the structure of the rhamnolipids was determined. The maximal vanadium removal efficiency (85.5%) was achieved with a rhamnolipids' concentration of 240 mg l^-1. The vanadium concentration was determined by spectroscopic technique. Rhamnolipids produced by this strain can potentially be used in the removal of vanadium.

Biomanagement of hexavalent chromium: Current trends and promising perspectives

Chromium (Cr) is most widely used heavy metal with vast applications in industrial sectors such as metallurgy, automobile, leather, electroplating, etc. Subsequently, these industries discharge large volumes of toxic Cr containing industrial wastewaters without proper treatment/management into the environment, causing severe damage to human health and ecology. This review gives some novel insights on the existing, successful and promising bio-based approaches for Cr remediation. In lieu of the multiple limitations of the physical and chemical methods for remediation, various biological means have been deciphered, wherein dead and live biomass have shown immense capabilities of removing/reducing and/or remediating Cr from polluted environmental niches. Adsorption of Cr by various agro-based waste and reduction/precipitation by different microbial groups have shown promising results in chromium removal/recovery. Various microbial based agents and aquatic plants like duckweeds are emerging as efficient adsorbents of metals and their role in chromium bioremediation is an effective green technology that needs to be harnessed effectively. The role of iron and sulphur reducing bacteria have shown potential for enhanced Cr remediation. Biosurfactants have revealed immense scope as enhancers of microbial metal bioremediation and have been reported to have potential for use in chromium recovery as well. The authors also explore the combined use of biochar and biosurfactants as a potential strategy for chromium bioremediation for the development of technology worth adopting. Cr is non-renewable and finite resource, therefore its safe removal/recovery from wastes is of major significance for achieving social, economic and environmental sustainability.

Bio-based rhamnolipids production and recovery from waste streams: Status and perspectives

Bio-based rhamnolipid production from waste streams is gaining momentum nowadays because of increasing market demand, huge range of applications and its economic and environment friendly nature. Rhamnolipid type biosurfactants are produced by microorganisms as secondary metabolites and have been used to reduce surface/interfacial tension between two different phases. Biosurfactants have been reported to be used as an alternative to chemical surfactants. Pseudomonas sp. has been frequently used for production of rhamnolipid. Various wastes can be used in production of rhamnolipid. Rhamnolipids are widely used in various industrial applications. The present review provides information about structure and nature of rhamnolipid, production using different waste materials and scale-up of rhamnolipid production. It also provides comprehensive literature on various industrial applications along with perspectives and challenges in this research area.

Use of waste canola oil as a low-cost substrate for rhamnolipid production using Pseudomonas aeruginosa

Rhamnolipids are glycolipid biosurfactants that are primarily produced by Pseudomonas aeruginosa that have gained a great deal of interest for their numerous industrial applications and environmentally friendly properties. In this study, we explored the potential of waste canola oil as a low-cost and environmentally friendly substrate for the production of rhamnolipids by P. aeruginosa. Four different 2³ full factorial designs were used to assess the effect of three independent factors on rhamnolipid production, including carbon source (canola oil and waste canola oil), nitrogen source [(NH₄)₂SO₄ and NaNO₃] and production time (7 and 14 days). The highest observed yield was 3585.31 ± 66.24 mg/L when P. aeruginosa was cultured for 14 days with 3% v/v waste canola oil and 4 g/L of NaNO₃. The nitrogen source proved to be a crucial factor, as the use of NaNO₃ rather than (NH₄)₂SO₄ led to a 30-fold increase in production yield. The observed yield when waste canola oil was used was similar to, and even slightly higher than, that obtained using canola oil. Our results showed that waste canola oil has great potential for use as a carbon source for rhamnolipid production by P. aeruginosa, thus paving the way for the development of a low-cost, efficient, and environmentally friendly bioprocess for the production of rhamnolipids.

Microbial production of rhamnolipids using sugars as carbon sources

Rhamnolipids are a class of biosurfactants with effective surface-active properties. The high cost of microbial production of rhamnolipids largely affects their commercial applications. To reduce the production post, research has been carried out in screening more powerful strains, engineering microbes with higher biosurfactant yields and exploring cheaper substrates to reduce the production cost. Extensive refining is required for biosurfactant production using oils and oil-containing wastes, necessitating the use of complex and expensive biosurfactant recovery methods such as extraction with solvents or acid precipitation. As raw materials normally can account for 10-30% of the overall production cost, sugars have been proven to be an alternative carbon source for microbial production of rhamnolipids due to its lower costs and straightforward processing techniques. Studies have thus been focused on using tropical agroindustrial crop residues as renewable substrates. Herein, we reviewed studies that are using sugar-containing substrates as carbon sources for producing rhamnolipids. We speculate that sugars derived from agricultural wastes rich in cellulose and sugar-containing wastes are potential carbon sources in fermentation while challenges still remain in large scales.