Effects of homemade biosurfactant from Bacillus methylotrophicus on bioremediation efficiency of a clay soil contaminated with diesel oil

Co-production of lipases and biosurfactants by Bacillus methylotrophicus in solid-state fermentation

The production of biosurfactants and lipases through solid-state fermentation (SSF) processes remains relatively unexplored, especially in bacterial applications. The use of solid matrices, eliminating the need for precipitation and recovery processes, holds significant potential for facilitating bioremediation. This study aimed to simultaneously produce biocompounds via SSF using Bacillus methylotrophicus and employ the fermented substrate for remediating soil contaminated with 20% biodiesel. Initial efforts focused on determining optimal conditions for concurrent lipase and biosurfactant production during an 8-day fermentation period. The selected conditions, including a substrate mix of wheat bran and corn cob (80/20), 75% moisture, 1% glycerol inducer, 2% nitrogen, and 1% sugarcane molasses, resulted in a 24.61% reduction in surface tension and lipase activity of 3.54 ± 1.20 U. Subsequently, a 90-day bioremediation of clayey soil contaminated with biodiesel showcased notable biodegradation, reaching 72.08 ± 0.36% within the initial 60 days. The incorporation of biocompounds, biostimulation, and bioaugmentation (Test E2) contributed to this efficacy. The use of the fermented substrate as a biostimulant and bioaugmentation agent facilitated in situ biocompound production in the soil, leading to a 23.97% reduction in surface tension and lipase production of 1.52 ± 0.19 U.

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03910-7.

Bacterial-derived surfactants: an update on general aspects and forthcoming applications

The search for sustainable alternatives to the production of chemicals using renewable substrates and natural processes has been widely encouraged. Microbial surfactants or biosurfactants are surface-active compounds synthesized by fungi, yeasts, and bacteria. Due to their great metabolic versatility, bacteria are the most traditional and well-known microbial surfactant producers, being Bacillus and Pseudomonas species their typical representatives. To be successfully applied in industry, surfactants need to maintain stability under the harsh environmental conditions present in manufacturing processes; thus, the prospection of biosurfactants derived from extremophiles is a promising strategy to the discovery of novel and useful molecules. Bacterial surfactants show interesting properties suitable for a range of applications in the oil industry, food, agriculture, pharmaceuticals, cosmetics, bioremediation, and more recently, nanotechnology. In addition, they can be synthesized using renewable resources as substrates, contributing to the circular economy and sustainability. The article presents a general and updated review of bacterial-derived biosurfactants, focusing on the potential of some groups that are still underexploited, as well as, recent trends and contributions of these versatile biomolecules to circular bioeconomy and nanotechnology.

Bubble Column Bioreactor using native non-genetically modified organisms: a remediation alternative by hydrocarbon-polluted water from the Gulf of Mexico

Notwithstanding the benefits that oil provides as a source of energy, society also recognizes the environmental problems caused by its use. We evaluated eight coastal sites in the central area of the Gulf of Mexico. At these sites, 14 hydrocarbons were detected which belong to compounds formed by carbons ranging from C9 to C27. The hydrocarbons with the highest concentrations were n-nonane (3.07 ± 1.60 mg L−1), carbazole (0.93 ± 0.12 mg L−1) and benzo [a] pyrene (1.33 ± 0.71 mg L−1). The hydrocarbons found belong mostly to medium fraction hydrocarbons, which are mostly found in fuels such as diesel. Therefore, this fuel was used as a carbon source or substrate in bubble column bioreactors. The capacity of non-genetically modified organisms to degrade microbial hydrocarbons was evaluated using a mineral medium for a period of 14 days. Suspended solids increased from 0.8 to 2.94 g L−1. Diesel consumption was achieved in 12 days of operation.

Microbial biosurfactants: a review of recent environmental applications

Microbial biosurfactants are low-molecular-weight surface-active compounds of high industrial interest owing to their chemical properties and stability under several environmental conditions. The chemistry of a biosurfactant and its production cost are defined by the selection of the producer microorganism, type of substrate, and purification strategy. Recently, biosurfactants have been applied to solve or contribute to solving some environmental problems, with this being their main field of application. The most referenced studies are based on the bioremediation of contaminated soils with recalcitrant pollutants, such as hydrocarbons or heavy metals. In the case of heavy metals, biosurfactants function as chelating agents owing to their binding capacity. However, the mechanism by which biosurfactants typically act in an environmental field is focused on their ability to reduce the surface tension, thus facilitating the emulsification and solubilization of certain pollutants (in-situ biostimulation and/or bioaugmentation). Moreover, despite the low toxicity of biosurfactants, they can also act as biocidal agents at certain doses, mainly at higher concentrations than their critical micellar concentration. More recently, biosurfactant production using alternative substrates, such as several types of organic waste and solid-state fermentation, has increased its applicability and research interest in a circular economy context. In this review, the most recent research publications on the use of biosurfactants in environmental applications as an alternative to conventional chemical surfactants are summarized and analyzed. Novel strategies using biosurfactants as agricultural and biocidal agents are also presented in this paper.

Recent advances in nanoremediation: Carving sustainable solution to clean-up polluted agriculture soils

Agriculture is one of the foremost significant human activities, which symbolizes the key source for food, fuel and fibers. This activity results in a lot of ecological harms particularly with the excessive usage of chemical fertilizers and pesticides. Different agricultural practices have remained industrialized to advance food production, due to the growth in the world population and to meet the food demand through the routine use of more effective fertilizers and pesticides. Soil is intensely embellished by environmental contamination and it can be stated as "universal incline." Soil pollution usually occurs from sewage wastes, accidental discharges or as byproducts of chemical residues of unrestrained production of numerous materials. Soil pollution with hazardous materials alters the physical, chemical, and biological properties, causing undesirable changes in soil fertility and ecosystem. Engineered nanomaterials offer various solutions for remediation of contaminated soils. Engineered nanomaterial-enable technologies are able to prevent the uncontrolled release of harmful materials into the environment along with capabilities to combat soil and groundwater borne pollutants. Currently, nanobiotechnology signifies a hopeful attitude to advance agronomic production and remediate polluted soils. Studies have outlined the way of nanomaterial applications to restore the eminence of the environment and assist the detection of polluted sites, along with potential remedies. This review focuses on the latest developments in agricultural nanobiotechnology and the tools developed to combat soil or land and or terrestrial pollution, as well as the benefits of using these tools to increase soil fertility and reduce potential toxicity.

Improving the Bioremediation and in situ Production of Biocompounds of a Biodiesel-Contaminated Soil

We aimed to produce simultaneously biosurfactants and lipases in solid state fermentation (SSF) using Aspergillus niger, followed by the use of the fermented media on the bioremediation of oily contaminated soil, in order to valuate agro industrial residuals and reduce the contamination. The biocompounds were produced using wheat bran and corncob (80:20), 5% of soybean oil and 0.5% of sugar cane molasses in SSF for 4 d, producing 4.58 ± 0.69 UE of emulsifying activity and 7.77 ± 1.52 U of lipolytic activity. This fermented media was used in the bioremediation of a 20% biodiesel contaminated soil, evaluating for 90 d microbial growth, contaminant degradation, and production of lipases and biosurfactants in soils. Six experimental strategies (natural attenuation; biostimulation + bioaugmentation + biocompounds; biostimulation + biosurfactant; biocompounds extract; biostimulation; adsorption of contaminant) were realized. The highest degradation of contaminant was verified in 90 d, of 74.40 ± 1.76%, and the production of biosurfactants and lipases in situ in the soil was found in 30 d (6.02 ± 0.24% of reduction in surface tension and 6.62 ± 0.17 UL of lipid activity in soil) for the same experiment (biostimulation + bioaugmentation + biocompounds). The addition of biostimulation + biosurfactant promotes higher biodegradation (66.00 ± 0.92%) of the contaminant than the biocompounds extract (59.58 ± 0.34%). The use of a solid fermented culture medium containing both biocompounds was feasible for the treatment of contaminants, demonstrating the potential for environmental application without the need for purification processes.

Bacterial biosurfactant increases ex situ biodiesel bioremediation in clayey soil

The contamination of soils by oily compounds has several environmental impacts, which can be reversed through bioremediation, using biosurfactants as auxiliaries in the biodegradation process. In this study, we aimed to perform ex situ bioremediation of biodiesel-contaminated soil using biosurfactants produced by Bacillus methylotrophicus. A crude biosurfactant was produced in a whey-based culture medium supplemented with nutrients and was later added to biodiesel-contaminated clayey soil. The produced lipopeptide biosurfactant could reduce the surface tension of the fermentation broth to 30.2 mN/m. An increase in the microbial population was observed in the contaminated soil; this finding can be corroborated by the finding of increased CO₂ release over days of bioremediation. Compared with natural attenuation, the addition of a lower concentration of the biosurfactant (0.5% w/w in relation to the mass of diesel oil) to the soil increased biodiesel removal by about 16% after 90 days. The added biosurfactant did not affect the retention of the contaminant in the soil, which is an important factor to be considered when applying in situ bioremediation technologies.

Development and Genetic Engineering of Hyper-Producing Microbial Strains for Improved Synthesis of Biosurfactants

Current research energies are fixated on the synthesis of environmentally friendly and non-hazardous products, which include finding and recognizing biosurfactants that can substitute synthetic surfactants. Microbial biosurfactants are surface-active compounds synthesized intracellularly or extracellularly. To use biosurfactants in various industries, it is essential to understand scientific engagements that demonstrate its potentials as real advancement in the 21st century. Other than applying a substantial effect on the world economic market, engineered hyper-producing microbial strains in combination with optimized cultivation parameters have made it probable for many industrial companies to receive the profits of 'green' biosurfactant innovation. There needs to be an emphasis on the worldwide state of biosurfactant synthesis, expression of biosurfactant genes in expressive host systems, the recent developments, and prospects in this line of research. Thus, molecular dynamics with respect to genetic engineering of biosynthetic genes are proposed as new biotechnological tools for development, improved synthesis, and applications of biosurfactants. For example, mutant and hyper-producing recombinants have been designed efficaciously to advance the nature, quantity, and quality of biosurfactants. The fastidious and deliberate investigation will prompt a comprehension of the molecular dynamics and phenomena in new microorganisms. Throughout the decade, valuable data on the molecular genetics of biosurfactant have been produced, and this solid foundation would encourage application-oriented yields of the biosurfactant production industry and expand its utilization in diverse fields. Therefore, the conversations among different interdisciplinary experts from various scientific interests such as microbiology, biochemistry, molecular biology, and genetics are indispensable and significant to accomplish these objectives.