Biosurfactant production by the hydrocarbon-degrading bacteria (HDB) Serratia marcescens : Optimization using central composite design (CCD)

An Insightful Overview of Microbial Biosurfactant: A Promising Next-Generation Biomolecule for Sustainable Future

Microbial biosurfactant is an emerging vital biomolecule of the 21st century. They are amphiphilic compounds produced by microorganisms and possess unique properties to reduce surface tension activity. The use of microbial surfactants spans most of the industrial fields due to their biodegradability, less toxicity, being environmentally safe, and being synthesized from renewable sources. These would be highly efficient eco-friendly alternatives to petroleum-derived surfactants that would open up new approaches to research on the production of biosurfactants. In the upcoming era, biobased surfactants will become a dominating multifunctional compound in the world market. Research on biosurfactants ranges from the search for novel microorganisms that can produce new molecules, structural and physiochemical characterization of biosurfactants, and fermentation process for enhanced large-scale productivity and green applications. The main goal of this review is to provide an overview of the recent state of knowledge and trends about microbially derived surfactants, various aspects of biosurfactant production, definition, properties, characteristics, diverse advances, and applications. This would lead a long way in the production of biosurfactants as globally successful biomolecules of the current century.

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.

Integrating phytoremediation and mycoremediation with biosurfactant-producing fungi for hydrocarbon removal and the potential production of secondary resources

Treatment of petroleum-contaminated soil to a less toxic medium via physical and chemical treatment is too costly and requires posttreatment. This review focuses on the employment of phytoremediation and mycoremediation technologies in cleaning hydrocarbon-contaminated soil which is currently rare. It is considered environmentally beneficial and possibly cost-effective as it implements the synergistic interaction between plants and biosurfactant producing mycorrhiza to degrade hydrocarbon contaminants. This review also covers possible sources of hydrocarbon pollution in water and soil, toxicity effects, and current technologies for hydrocarbon removal and degradation. In addition to these problems, this review also discusses the challenges and opportunities of transforming the resultant treated sludge and treating plants into potential by-products for a higher quality of life for future generations.

Synthesis and Optimization of Glycerol Carbonate from Crude Glycerol Using Sodium Carbonate (Na2CO3) as a Heterogeneous Catalyst

The essential need for sustainable energy sources to replace fossil fuels has fueled interest in renewable energy and biorefinery processes. Biodiesel production generates a considerable amount of crude glycerol (CG), which poses a challenge for the industry. This study aims to address this challenge by purifying CG through acidification. The acidification process successfully purified crude glycerol (PCG), resulting in a purity of 98.4 wt %. Subsequently, synthesizing glycerol carbonate (GC) from PCG and dimethyl carbonate (DMC) was undertaken by using heterogeneous catalysts. Sodium carbonate (Na2CO3) emerges as the most promising catalyst, considering its suitability in the presence of impurities such as 0.72 wt % of water and 0.57 wt % of matter organic nonglycerol (MONG) in PCG. The optimum catalyst dosage of Na2CO3 was determined as 2.1% mol of PCG. The experiments were carried out using a central composite design (CCD) methodology. By employing the response surface method (RSM), the optimal reaction conditions were determined to be a PCG/DMC molar ratio of 1:2.37 and a reaction time of 1.83 h. Under these conditions, an observed GC yield of 72.13% and PCG conversion of 78.39% were achieved. Despite the purification process, PCG still contains residual water, making Na2CO3 a suitable catalyst capable of tolerating a water content up to 3 wt %. This study not only enhances the effective utilization of CG within the biodiesel industry but also offers valuable insights for further exploration of sustainable chemical processes in future research.

Response Surface Methodology for the Optimization of Zn-Contaminated Soil Remediation by Soil Washing with Water-Soluble Chitosan

Soil washing is an important method for the remediation of contaminated soil. This research presents the optimization of soil washing conditions in the remediation of Zn-contaminated soils with water-soluble chitosan (WSCS). Response surface methodology (RSM) was used to optimized the washing conditions after single factor experiments. The central composite design (CCD) with three factors and five levels was applied to the optimization of the removal efficiency of Zn from soils, and WSCS concentration, pH value, and washing time were evaluated variables in the washing process. Results indicated that the pH value (p < 0.0001) was the most significant factor which mainly affected the distribution and content of metal species in aqueous solution, ion exchange and adsorption/desorption behavior of metals, solubility of chelating agent, as well as readsorption of metal complexes. The optimal conditions for the Zn removal from soils were WSCS concentration of 1.5%, pH of 3.3, and washing time of 72 min. The removal efficiency could reach 65.4% under the optimized conditions, which was close to the predicted value of 68.3% by the response surface method. Therefore, it could be found that the response surface methodology was an effective method to determine the optimal conditions for the removal of metals from contaminated soils by soil washing.

Novel production of biodispersant by Serratia marcescens UCP 1549 in solid-state fermentation and application for oil spill bioremediation

Oil spills in aquatic ecosystems cause irreparable damage to marine life and the coastal populations of affected areas. In recent years, chemical dispersants have been extensively used to remedy these impacted ecosystems, although these agents have been increasingly restricted due to their toxic potential. In this context, biosurfactants are emerging as a promising alternative to chemical dispersants, which have some advantages including low toxicity, high biodegradability and good ecological acceptability. Thus, this study aimed to the production of biosurfactant by the bacteria Serratia marcescens UCP 1549 for application as biodispersant. The experiment was carried out using wheat bran as substrate in solid-state fermentation (SSF) as low-cost technology. Biosurfactant production was verified by the reduction of surface tension (28.4 mN/m) and interfacial tension (4.1 mN/m) with n-hexadecane. Also, promising result of emulsification (94%) with burned motor oil was obtained. Acid precipitation yielded 52.0 g/kg dry substrate of biosurfactant, that was identified as an anionic compound of a lipopeptide nature by the Zeta potential and FTIR spectrum, respectively. The biomolecule showed stability under extreme conditions of temperature, pH and salinity, as well as low toxicity against the microcrustacean Artemia salina. In addition, the biosurfactant demonstrated excellent properties to dispersing burned motor oil in water (ODA = 50.24 cm²) and to washing of marine stones (100% removal of burned motor oil). Therefore, these results confirm SSF as a sustainable technology for the production of biodispersant by S. marcescens UCP 1549, promising in the bioremediation of marine ecosystems impacted by petroderivatives.

Remediation of petroleum hydrocarbons-contaminated soil: Analysis based on Chinese patents

Increasing soil petroleum hydrocarbons (PHs) pollution have caused world-wide concerns. The removal of PHs from soils mainly involves physical, chemical, biological processes and their combinations. To date, most reviews in this field based on research articles, but limited papers focused on the integration of remediation technologies from the perspective of patents. In this study, 20-years Chinese patents related to the remediation of soil PHs were comprehensively analyzed. It showed an increasing number of patent applications and the patents' quantity were positively correlated with Chinese GDP over the years, suggesting the more the economy developed the more environmental problems and corresponding solutions emerged. In addition, chemical technologies were mostly used in a combination to achieve faster and better effects, while the physical technologies were often used alone due to high costs. In all PHs remediation techniques, bacteria-based bioremediation was the most used from 2000 to 2019. Bacillus spp. and Pseudomonas spp. were the most used bacteria for PHs treatment because these taxa were widely harboring functions such as biosurfactant production and hydrocarbon degradation. The future research on joint technologies combining microbial and physicochemical ones for better remediation effect and application are highly encouraged.

Lipopeptide production by Serratia marcescens SmSA using a Taguchi design and its application in enhanced heavy oil recovery

Biosurfactant production at reactor level by Serratia marcescens SmSA was optimized and evaluated to enhance the heavy oil recovery on carbonate rocks. Temperature, agitation, and carbon/nitrogen (C/N) ratio were evaluated to optimize biosurfactant production by using a Taguchi (L9) design. The best conditions (C/N ratio: 6, 25 °C, and agitation: 100 rpm) were used to scale up the biosurfactant production with a 3-L bioreactor. The best aeration for biosurfactant production was 0.66 volume of air per volume of liquid per minute (vvm), producing the lowest surface tension (26 mN/m) in 14 h, with a biosurfactant yield of 14.26 g/L as a crude product and 2.85 g/L as a purified product, and a critical micelle concentration of 280 mg/L. The biosurfactant was characterized as a lipopeptide, and it was stable under extreme conditions: pH (2-12), salinity up to 200 g/L, and temperature up to 150 °C confirmed by thermogravimetric analysis. Enhanced oil recovery test was carried out with a carbonate core and heavy oil under reservoir conditions, obtaining an additional recovery of 8%, due to reduced interfacial tension and modified wettability of the rock. These findings highlight the potential application of S. marcescens SmSA biosurfactant in enhanced oil recovery.

Statistical optimization of biosurfactant production using waste biomaterial and biosorption of Pb2+ under concomitant submerged fermentation

The present study was conducted to statistically optimize the biosurfactant production yield of Pseudomonas sp. F5 using raw orange peel extract (Central composite design (CCD) design; Surface tension (ST) reduction = 32.41 dyne/cm; biosurfactant yield = ~2.4 g/L). The extracted biosurfactant was characterized as a glycolipid having predominant mono-rhamnolipids than di-rhamnolipids with a critical micelle concentration (CMC) of 40 mg/L. The potential of strain F5 for good biosurfactant yield during Pb²⁺ stress and the inherent mechanism for simultaneous biosorption of Pb²⁺ was also investigated. During concomitant submerged fermentation from 100 to 500 mg/L of Pb²⁺ showed enhancement in adsorption capacity from 99.44 to 267.86 mg/g respectively having 60.33 ± 2.87 of emulsification index (E₂₄%) measured at 100 mg/L Pb²⁺ corresponding to maximum biosurfactant production during metal stress. The bacterium showed a high Pb²⁺ MIC (minimum inhibitory concentration) of 2200 mg/L and efficiently biosorbed Pb²⁺ ions at pH 7 and a dosage of 0.05 g under varying initial metal ion concentration and contact time. The exothermic biosorption (chemisorption) mechanism was found to be fitted well with Langmuir (R² = 0.9859) and Pseudo second-order kinetic model (R² = 0.9975; 200 mg/L) having a maximum adsorption capacity of 294.12 mg/g. These findings indicated the excellent potential of biosurfactant producing strain F5 in the removal of Pb²⁺ ions from aqueous system and management of agrowastes as suitable carbon substrate.

Microbial Biosurfactant: A New Frontier for Sustainable Agriculture and Pharmaceutical Industries

In the current scenario of changing climatic conditions and the rising global population, there is an urgent need to explore novel, efficient, and economical natural products for the benefit of humankind. Biosurfactants are one of the latest explored microbial synthesized biomolecules that have been used in numerous fields, including agriculture, pharmaceuticals, cosmetics, food processing, and environment-cleaning industries, as a source of raw materials, for the lubrication, wetting, foaming, emulsions formulations, and as stabilizing dispersions. The amphiphilic nature of biosurfactants have shown to be a great advantage, distributing themselves into two immiscible surfaces by reducing the interfacial surface tension and increasing the solubility of hydrophobic compounds. Furthermore, their eco-friendly nature, low or even no toxic nature, durability at higher temperatures, and ability to withstand a wide range of pH fluctuations make microbial surfactants preferable compared to their chemical counterparts. Additionally, biosurfactants can obviate the oxidation flow by eliciting antioxidant properties, antimicrobial and anticancer activities, and drug delivery systems, further broadening their applicability in the food and pharmaceutical industries. Nowadays, biosurfactants have been broadly utilized to improve the soil quality by improving the concentration of trace elements and have either been mixed with pesticides or applied singly on the plant surfaces for plant disease management. In the present review, we summarize the latest research on microbial synthesized biosurfactant compounds, the limiting factors of biosurfactant production, their application in improving soil quality and plant disease management, and their use as antioxidant or antimicrobial compounds in the pharmaceutical industries.

Optimization of biosurfactant production from Pseudomonas sp. CQ2 and its application for remediation of heavy metal contaminated soil

The present study was conducted to enhance the biosurfactant production yield of Pseudomonas sp. CQ2 isolated from the Chongqing oilfield (China). Besides, the capability of biosurfactant and underlying mechanism for remediation of heavy metal contaminated soil was also investigated. Our results suggested that maximum biosurfactant production (40.7 g/L) was attained at 35 °C by using soybean oil and ammonium nitrate as carbon and nitrogen sources with pH 7, rotational speed of 175 rpm and inoculation ratio of 3%). The removal efficiencies of 78.7, 65.7 and 56.9% for Cd, Cu and Pb respectively were achieved at optimized bioleaching conditions (pH: 11, soil/solution ratio: 30:1 and non-sterilized soil), comparative tests between common chemical surfactants (SDS, Tween-80) and biosurfactants demonstrated the larger removal capacity of biosurfactants. Through SEM-EDX, it was found that the granular material disappeared, the content of Cd, Cu and Pb decreased significantly, and the soil surface became smooth with hole formation after soil washing following bioleaching. ATR-FTIR results showed that the carboxyl functional groups in biosurfactants could chelate heavy metals. These results indicated that biosurfactants from Pseudomonas sp. CQ2 could effectively eliminate Cd, Cu, and Pb from soil.

Ozone Degradation of Prometryn in Ruditapes philippinarum: Response Surface Methodology Optimization and Toxicity Assessment

ABSTRACT

This study optimized the method for ozone (O3) degradation of prometryn in the clam Ruditapes philippinarum and evaluated toxicity changes during ozone degradation. The gas chromatography method for the detection of prometryn was appropriately improved. The linear range was 5 to 500 ng/mL, with a correlation coefficient of 0.9964. The addition concentration of prometryn was 0.025 to 0.100 mg/kg, the recovery was 77.97 to 85.00%, the relative standard deviation (n = 6) was 2.36 to 7.86%, and the limit of detection was 0.3 μg/kg. Using the central composite design in two experiments, ozone as gas and ozone dissolved in water, the effect of degradation rate was studied on three variables: ozone concentration, temperature, and exposure time. Ozone as gas and ozone dissolved in water have the same degradation effect on prometryn. The O3 concentration was 4.2 mg/L, the temperature was 40°C, the exposure time was 10 min, and the maximum degradation rate was 89.94 and 89.69% for the two experiments, respectively. In addition, the toxicity of ozone degradation products was evaluated using buffalo rat liver cells. After ozone treatment for 30 min, the toxicity of the ozone degradation products was reduced to 52.15% compared with that of prometryn itself. The toxicity of the ozone degradation products increased slightly when the ozonation time was prolonged; the toxicity at 180 min was greater than that of the parent compound prometryn. Overall, the application of ozone degradation of pesticide residues is a promising new technology. This study determined better degradation conditions for prometryn in R. philippinarum and also provided a theoretical basis for the widespread use of ozone technology in the future.

HIGHLIGHTS

Application of Biosurfactants and Pulsating Electrode Configurations as Potential Enhancers for Electrokinetic Remediation of Petrochemical Contaminated Soil

The remediation of soil contaminated with petrochemicals using conventional methods is very difficult because of the complex emulsions formed by solids, oil, and water. Electrokinetic remediation has of recent shown promising potential in the removal of organics from contaminated media as calls for further improvement of the technology are still made. This work investigated the performance of electrokinetic remediation of soil contaminated with petrochemicals by applying fixed electrode configurations and continuous approaching electrode configurations. This was done in combination with bioremediation by inoculating hydrocarbon degrading bacteria and biosurfactants with the aim of obtaining an improved method of remediation. The results obtained show that the biosurfactant produced by the hydrocarbon degrading bacteria Pseudomonas aeruginosa was able to enhance oil extraction to 74.72 ± 2.87%, 57.375 ± 3.75%, and 46.2 ± 4.39% for 185 mm fixed electrodes, 335-260-185 mm continuous approaching electrodes, and 335 mm fixed electrode configurations, respectively. By maintaining high current flow, the 335-260-185 mm continuous approaching electrodes configuration enhanced electroosmotic flow (EOF) on every event of electrodes movement. The fixed electrode configuration of 185 mm provided amiable pH conditions for bacterial growth by allowing quick neutrality of the pH due to high EOF as compared to the 335 mm fixed electrodes configuration. After 240 h, the carbon content in the soil was reduced from 0.428 ± 0.11 mg of carbon/mg of the soil to 0.103 ± 0.005, 0.11355 ± 0.0006, and 0.1309 ± 0.004 for 185 mm, 335-260-185 mm, and 335 mm, respectively. The application of biosurfactants and continuous approaching electrodes reduced the energy expenditure of electrokinetic remediation by enhancing the decontamination process with respect to time.

Plant-assisted remediation of hydrocarbons in water and soil: Application, mechanisms, challenges and opportunities

Due to the increasing importance of diesel and petroleum for industrial development during the last century, petrochemical effluents have significantly contributed to the pollution of aquatic and soil environments. The contamination generated by petroleum hydrocarbons can endanger not only humans but also the environment. Phytoremediation or plant-assisted remediation can be considered one of the best technologies to manage petroleum product-contaminated water and soil. The main advantages of this method are that it is environmentally-friendly, potentially cost-effective and does not require specialised equipment. The scope of this review includes a description of hydrocarbon pollutants from petrochemical industries, their toxicity impacts and methods of treatment and degradation. The major emphasis is on phytodegradation (phytotransformation) and rhizodegradation since these mechanisms are the most favourable alternatives for soil and water reclamation of hydrocarbons using tropical plants. In addressing these issues, this review also covers challenges to retrieve the environment (soil and water) from petroleum contaminations through phytoremediation, and its opportunities to remove or reduce the negative environmental impacts of petroleum contaminations and restore damaged ecosystems with sustainable ways to keep healthy life for the future.

A newly isolated strain of Serratia sp. from an oil spillage site of Assam shows excellent bioremediation potential

A hydrocarbon-degrading strain was isolated from a petroleum oil-contaminated site which was identified on the basis of 16S rDNA gene sequencing as a member of the genus Serratia. The isolate reduced surface tension of petroleum oil supplemented medium by 48.35% with respect to control after 7 days of treatment. Fluorescence microscopy revealed that its chemotaxis was towards hydrocarbon. The isolate degraded 87.54 and 85.48% of diesel and kerosene in liquid culture, respectively, after 28 day incubation at 37 ± 2 °C. The ex situ pilot scale bioremediation experiment in which artificially contaminated soil (10 and 20% v/w kerosene) was treated for 7 days showed a germination rate of Vigna radiate seeds of 52% and 72%, respectively. Interestingly, a germination rate of 31% was obtained with the heavily contaminated soil samples collected from the oil spillage site after 20 days of bioremediation treatment. The presence of υ_CH3 (asymmetric stretching), υ_C=C (stretch), and υ_C-C (stretch) in the crude biosurfactant produced by the isolate was revealed by FTIR analysis, and emulsification index (E ₂₄) was found 60 and 56.6%, respectively, against diesel and kerosene oil. The non-cytotoxicity nature of the biosurfactant also supports its potential application in field trial.

Overproduction of rhamnolipid by fed-batch cultivation of Pseudomonas aeruginosa in a lab-scale fermenter under tight DO control

Rhamnolipids are one of the most well-known classes of biosurfactants having wide applications in various industries due to low toxicity, high biodegradability, and environmentally friendly. Dissolved oxygen (DO) concentration has the crucial effect on rhamnolipids production, particularly through fed-batch cultivation. In this study, the effect of different levels of DO concentrations on rhamnolipid production by Pseudomonas aeruginosa in both batch and fed-batch fermentation was investigated in a lab-scale fermenter under precise DO control. A maximal rhamnolipid production of 22.5 g/l was obtained at a DO concentration of 40% in batch fermentation. In order to achieve the high rhamnolipid production, a fed-batch operation under tight DO control of 40% was conducted. As a result, the overall rhamnolipid production and productivity reached to 240 g/l and 0.9 (g/l h), corresponding to a 10.7 and 4.8-fold improvement compared to the batch experiments. The high level of rhamnolipid production via the fed-batch cultivation can be attributed to both DO concentration and the feeding strategy. This achievement is promising for the production of rhamnolipid in industrial scale.

Isolation and characterization of biosurfactant-producing and diesel oil degrading Pseudomonas sp. CQ2 from Changqing oil field, China

In the present research investigation, 13 indigenous bacteria (from CQ1 to CQ13) were isolated from soil collected from Changqing oil field of Xi'an, China. Four promising biosurfactant producers (CQ1, CQ2, CQ4, and CQ13) were selected through primary screening among these 13 strains, including via drop collapse and oil-spreading methods. However, only the strain CQ2 showed the best biosurfactant production and was further screened by hemolytic assay, cetyl trimethyl ammonium bromide (CTAB), surface tension and emulsifying activity. The bacterium CQ2 has the ability to produce about 3.015 g L-1 of biosurfactant using glucose as the sole carbon source without any optimization. The produced biosurfactant could greatly reduce surface tension from 72.66 to 24.72 mN m-1 with a critical micelle concentration (CMC) of 30 mg L-1 and emulsify diesel oil up to 60.1%. The cell-free broth was found to be stable in wide temperature (4-100 °C), pH (6-12) and salinity (2-20%) ranges for surface and emulsifying activity. This biosurfactant was preliminarily found to be of a glycolipid nature as evident from thin-layer chromatographic (TLC) and Fourier transform infra-red spectroscopic (FTIR) analyses. Moreover, CQ2 was able to degrade 54.7% of diesel oil, which surprisingly could form a substantial amount of bioflocculants during the degradation process. Furthermore, the 16S rDNA sequence using the Genbank BLAST tool revealed that isolated CQ2 was closely related to species of Pseudomonas genus and, thus, was entitled Pseudomonas sp. CQ2. The results of residual diesel oil contents measured by GC-MS showed that C7-C28 hydrocarbons could be degraded by Pseudomonas sp. CQ2. Thus, these findings revealed that CQ2 could be applied for remediation of diesel oil/petroleum-contaminated waters and soils on a large scale.

Optimization of Conditions for Extraction of Polyphenols and the Determination of the Impact of Cooking on Total Polyphenolic, Antioxidant, and Anticholinesterase Activities of Potato

In this work we optimized the cooking and extraction conditions for obtaining high yields of total polyphenols from potato and studied the effect of three domestic methods of cooking on total phenols, antioxidant activity, and anticholinesterase activities. The optimization of the experiment was carried out by the experimental designs. The extraction of the polyphenols was carried out by maceration and ultrasonication. Determination of the polyphenols was performed by using the Folin-Ciocalteau reagent method. The antioxidant activity was evaluated by three methods: 1,1-diphenyl-2-picryl-hydrazyl (DPPH), 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS), and CUPRAC(Cupric reducing antioxidant capacity), the anticholinesterase activity was evaluated by the method of Elmann. The optimum of total phenolic obtained was: 4.668 × 10⁴, 1.406 × 10⁴, 3357.009, 16,208.99 µg Gallic Acid Equivalent (GAE)/g of dry extract for crude potato, steamed potatoes, in boiling water, and by microwave, respectively. The three modes of cooking cause a decrease in the total polyphenol contents, antioxidant and anticholinesterase activities.