Optimization of biosurfactant production from chemically mutated strain of Bacillus subtilis using waste automobile oil as low-cost substrate

Biological machinery for the production of biosurfactant and their potential applications

The growing biotechnology industry has focused a lot of attention on biosurfactants because of several advantages over synthetic surfactants. These benefits include worldwide public health, environmental sustainability, and the increasing demand from sectors for environmentally friendly products. Replacement with biosurfactants can reduce upto 8% lifetime CO2 emissions avoiding about 1.5 million tons of greenhouse gas released into the atmosphere. Therefore, the demand for biosurfactants has risen sharply occupying about 10% (∼10 million tons/year) of the world production of surfactants. Biosurfactants' distinct amphipathic structure, which is made up of both hydrophilic and hydrophobic components, enables these molecules to perform essential functions in emulsification, foam formation, detergency, and oil dispersion-all of which are highly valued characteristic in a variety of sectors. Today, a variety of biosurfactants are manufactured on a commercial scale for use in the food, petroleum, and agricultural industries, as well as the pharmaceutical and cosmetic industries. We provide a thorough analysis of the body of knowledge on microbial biosurfactants that has been gained over time in this research. We also discuss the benefits and obstacles that need to be overcome for the effective development and use of biosurfactants, as well as their present and future industrial uses.

Bacillus genus industrial applications and innovation: First steps towards a circular bioeconomy

In recent decades, environmental concerns have directed several policies, investments, and production processes. The search for sustainable and eco-friendly strategies is constantly increasing to reduce petrochemical product utilization, fossil fuel pollution, waste generation, and other major ecological impacts. The concepts of circular economy, bioeconomy, and biorefinery are increasingly being applied to solve or reduce those problems, directing us towards a greener future. Within the biotechnology field, the Bacillus genus of bacteria presents extremely versatile microorganisms capable of producing a great variety of products with little to no dependency on petrochemicals. They are able to grow in different agro-industrial wastes and extreme conditions, resulting in healthy and environmentally friendly products, such as foods, feeds, probiotics, plant growth promoters, biocides, enzymes, and bioactive compounds. The objective of this review was to compile the variety of products that can be produced with Bacillus cells, using the concepts of biorefinery and circular economy as the scope to search for greener alternatives to each production method and providing market and bioeconomy ideas of global production. Although the genus is extensively used in industry, little information is available on its large-scale production, and there is little current data regarding bioeconomy and circular economy parameters for the bacteria. Therefore, as this work gathers several products' economic, production, and environmentally friendly use information, it can be addressed as one of the first steps towards those sustainable strategies. Additionally, an extensive patent search was conducted, focusing on products that contain or are produced by the Bacillus genus, providing an indication of global technology development and direction of the bacteria products. The Bacillus global market represented at least $18 billion in 2020, taking into account only the products addressed in this article, and at least 650 patent documents submitted per year since 2017, indicating this market's extreme importance. The data we provide in this article can be used as a base for further studies in bioeconomy and circular economy and show the genus is a promising candidate for a greener and more sustainable future.

Microbial Biosurfactant: Candida bombicola as a Potential Remediator of Environments Contaminated by Heavy Metals

Industrial interest in surfactants of microbial origin has intensified recently due to the characteristics of these compounds, such as biodegradability and reduced toxicity, and their efficiency in removing heavy metals and hydrophobic organic compounds from soils and waters. The aim of this study was to produce a biosurfactant using Candida bombicola URM 3712 in a low-cost medium containing 5.0% molasses, 3.0% corn steep liquor and 2.5% residual frying oil for 144 h at 200 rmp. Measurements of engine oil tension and emulsification were made under extreme conditions of temperature (0 °C, 5 °C, 70 °C, 100 °C and 120 °C), pH (2-12) and NaCl concentrations (2-12), demonstrating the stability of the biosurfactant. The isolated biosurfactant was characterized as an anionic molecule with the ability to reduce the surface tension of water from 72 to 29 mN/m, with a critical micellar concentration of 0.5%. The biosurfactant had no toxic effect on vegetable seeds or on Eisenia fetida as a bioindicator. Applications in the removal of heavy metals from contaminated soils under dynamic conditions demonstrated the potential of the crude and isolated biosurfactant in the removal of Fe, Zn and Pb with percentages between 70 and 88%, with the highest removal of Pb being 48%. The highest percentage of removal was obtained using the cell-free metabolic liquid, which was able to remove 48, 71 and 88% of lead, zinc and iron from the soil, respectively. Tests in packed columns also confirmed the biosurfactant's ability to remove Fe, Zn and Pb between 40 and 65%. The removal kinetics demonstrated an increasing percentage, reaching removal of 50, 70 and 85% for Pb, Zn and Fe, respectively, reaching a greater removal efficiency at the end of 24 h. The biosurfactant was also able to significantly reduce the electrical conductivity of solutions containing heavy metals. The biosurfactant produced by Candida bombicola has potential as an adjuvant in industrial processes for remediating soils and effluents polluted by inorganic contaminants.

A comprehensive study on microbial-surfactants from bioproduction scale-up toward electrokinetics remediation of environmental pollutants: Challenges and perspectives

Currently, researchers have focused on electrokinetic (EK) bioremediation due to its potential to remove a wide-range of pollutants. Further, to improve their performance, synthetic surfactants are employed as effective additives because of their excellent solubility and mobility. Synthetic surfactants have an excessive position in industries since they are well-established, cheap, and easily available. Nevertheless, these surfactants have adverse environmental effects and could be detrimental to aquatic and terrestrial life. Owing to social and environmental awareness, there is a rising demand for bio-based surfactants in the global market, from environmental sustainability to public health, because of their excellent surface and interfacial activity, higher and stable emulsifying property, biodegradability, non- or low toxicity, better selectivity and specificity at extreme environmental conditions. Unfortunately, challenges to biosurfactants, like expensive raw materials, low yields, and purification processes, hinder their applicability to large-scale. To date, extensive research has already been conducted for production scale-up using multidisciplinary approaches. However, it is still essential to research and develop high-yielding bacteria for bioproduction through traditional and biotechnological advances to reduce production costs. Herein, this review evaluates the recent progress made on microbial-surfactants for bioproduction scale-up and provides detailed information on traditional and advanced genetic engineering approaches for cost-effective bioproduction. Furthermore, this study emphasized the role of electrokinetic (EK) bioremediation and discussed the application of BioS-mediated EK for various pollutants remediation.

Sustainable Production of Biosurfactant from Agro-Industrial Oil Wastes by Bacillus subtilis and Its Potential Application as Antioxidant and ACE Inhibitor

The microbial conversion of agro-industrial oil wastes into biosurfactants shows promise as a biomass refinery approach. In this study, Bacillus subtilis #309 was applied to produce surfactin using rapeseed and sunflower cakes, the most common oil processing side products in Europe. Studies of the chemical composition of the substrates were performed, to determine the feasibility of oil cakes for surfactin production. Initially, screening of proteolytic and lipolytic activity was performed to establish the capability of B. subtilis #309 for substrate utilization and hence effective surfactin production. B. subtilis #309 showed both proteolytic and lipolytic activity. The process of surfactin production was carefully analyzed by measurement of the surfactin concentration, pH, surface tension (ST) and emulsification index (E₂₄). The maximal surfactin concentration in the sunflower and rapeseed cake medium reached 1.19 ± 0.03 and 1.45 ± 0.09 g/L, respectively. At the same time, a progressive decrease in the surface tension and increase in emulsification activity were observed. The results confirmed the occurrence of various surfactin homologues, while the surfactin C₁₅ was the dominant one. Finally, the analysis of surfactin biological function exhibited antioxidant activity and significant angiotensin-converting enzyme (ACE)-inhibitory activity. The half-maximal inhibitory concentration (IC₅₀) value for ACE inhibition was found to be 0.62 mg/mL for surfactin. Molecular docking of the surfactin molecule to the ACE domains confirmed its inhibitory activity against ACE. Several interactions, such as hydrophobic terms, hydrogen bonds and van der Waals interactions, were involved in the complex stabilization. To the best of our knowledge, this is the first report describing the effect of a lipopeptide biosurfactant, surfactin, produced by B. subtilis for multifunctional properties in vitro, namely the ACE-inhibitory activity and the antioxidant properties, using different assays, such as 2,2-azinobis (3-ethyl-benzothiazoline-6-sulfonic acid (ABTS), 2,2-diphenyl-1-picrylhydrazyl (DPPH) and ferric reducing antioxidant power (FRAP). Thus, the ACE-inhibitory lipopeptide biosurfactant shows promise to be used as a natural antihypertensive agent.

Biosurfactant production prospects of a Gram-negative bacterium-Klebsiella pneumoniae ssp. ozaenae BK34

Increasing environmental concerns have brought natural surfactant produced by microorganisms into limelight due to their lesser toxicity, biodegradable nature, and retention of activity at extreme conditions. In the present investigation, the surfactant production perspective of capsulated Gram-negative bacilli Klebsiella pneumoniae ssp. ozaenae BK34 was explored. It was identified on the basis of PCR amplification of conserved region of 16SrRNA using species specific primers. Highest oil displacement and emulsification (E₂₄) index of 6.8 cm and 20% along with 4.38-fold increase in biomass were attained using olive oil (2% (v/v)) as substrate. Incorporation of urea at 0.5% (w/v) concentration increased the oil displacement, E₂₄ index, and drop diameter to 9.2 cm, 77.50%, and 0.80 cm, respectively, accompanied by 5.38-fold increase in biomass production. Biosurfactant level was recorded maximum at 30 °C as apparent from the oil displacement of 9.3 cm and E₂₄ index of 75%. Reduction in incubation temperature to 25 °C abated oil displacement (5.2 cm) and E₂₄ index (17.66%). Biosurfactant production was also appeared to be pH sensitive as shifting pH from 7.0 to 6.0 or 8.0 reduced the E₂₄ index from 75 to 35% and 25%, respectively. Inoculum of stationary phase bacterial biomass at the proportion of 0.05% (w/v) was found adequate in triggering maximum biosurfactant production while the log phase biomass delayed the production significantly. Acid precipitation method was able to yield 7 g/L biosurfactant at pH 2. The surfactant was allocated to glycolipopeptide class on the basis of FTIR spectroscopy.

Cellulose-deconstruction potential of nano-biocatalytic systems: A strategic drive from designing to sustainable applications of immobilized cellulases

Nanostructured materials along with an added value of polymers-based support carriers have gained high interest and considered ideal for enzyme immobilization. The recently emerged nanoscience interface in the form of nanostructured materials combined with immobilized-enzyme-based bio-catalysis has now become research and development frontiers in advance and applied bio-catalysis engineering. With the involvement of nanoscience, various polymers have been thoroughly developed and exploited to nanostructured engineer constructs as ideal support carriers/matrices. Such nanotechnologically engineered support carriers/matrix possesses unique structural, physicochemical, and functional attributes which equilibrate principal factors and strengthen the biocatalysts efficacy for multipurpose applications. In addition, nano-supported catalysts are potential alternatives that can outstrip several limitations of conventional biocatalysts, such as reduced catalytic efficacy and turnover, low mass transfer efficiency, instability during the reaction, and most importantly, partial, or complete inhibition/deactivation. In this context, engineering robust and highly efficient biocatalysts is an industrially relevant prerequisite. This review comprehensively covered various biopolymers and nanostructured materials, including silica, hybrid nanoflower, nanotubes or nanofibers, nanomembranes, graphene oxide nanoparticles, metal-oxide frameworks, and magnetic nanoparticles as robust matrices for cellulase immobilization. The work is further enriched by spotlighting applied and industrially relevant considerations of nano-immobilized cellulases. For instance, owing to the cellulose-deconstruction features of nano-immobilized cellulases, the applications like lignocellulosic biomass conversion into industrially useful products or biofuels, improved paper sheet density and pulp beat in paper and pulp industry, fruit juice clarification in food industry are evident examples of cellulases, thereof are discussed in this work.

Robust nanocarriers to engineer nanobiocatalysts for bioprocessing applications

The synergistic integration of bio-catalysis engineering with nanostructured materials, as unique multifunctional carrier matrices, has emerged as a new interface of nanobiocatalysis (NBC). NBC is an emerging innovation that offers significant considerations to expand the designing and fabrication of robust catalysts at the nanoscale with improved catalytic characteristics for multipurpose bioprocessing applications. In addition, nanostructured materials with unique structural, physical, chemical, and functional entities have manifested significant contributions in mimicking the enzyme microenvironment. A fine-tuned enzyme microenvironment with an added-value of NBC offers chemo- regio- and stereo- selectivities and specificities. Furthermore, NBC is growing rapidly and will become a powerful norm in bio-catalysis with much controlled features, such as selectivity, specificity, stability, resistivity, induce activity, reaction efficacy, multi-usability, improved mass transfer efficiency, high catalytic turnover, optimal yield, ease in recovery, and cost-effectiveness. Considering the above critics and unique structural, physicochemical, and functional attributes, herein, we present and discuss advances in NBC and its bioprocessing applications in different fields. Briefly, this review is focused on four parts, i.e., (1) NBC as a drive towards applied nanobiocatalysts (as an introduction with opportunities), (2) promising nanocarriers to develop nanobiocatalysts, (3) applications in the fields of biotransformation, biofuel production, carbohydrate hydrolysis, bio-/nanosensing, detergent formulations, and extraction and purification of value-added compounds, and (4) current challenges, concluding remarks, and future trends.

Metagenomic analysis of microbial community and its role in bioelectrokinetic remediation of tannery contaminated soil

Tanneries create a serious threat to the environment by generating a significant amount of toxic metal-containing solid waste. This study deals with the application of bio-electrokinetic remediation (Bio-EK) of tannery effluent contaminated soil (TECS). Metagenomes representing the TECS sample were sequenced using the Illumina HiSeq platform. The bioreduction of hexavalent chromium Cr(VI)to trivalent chromium Cr (III) was achieved by BIO-EK techniques. NGS-data (Next Generation Sequencing) analysis was revealed that Proteobacteria, Firmicutes, Bacteroidetes, Actinobacteria, and Planctomycetes were identified in the bio-electrokinetic system. Proteobacteria are responsible for the bioreduction of chromium hexavalent by the formation of FeS particles. The bio-generated FeS particles can be reduced the toxic chromium (VI) to non-toxic chromium (III) in soil. Simultaneously total chromium and organic content were significantly removed in BIO-EK (40 and 290 mg kg^-1) when compared to control soil (182 and 240 mg kg^-1). The presence of pollutant degrading microbes such as Desulfovibrio, Pseudomonas, Bacillus, Clostridium, Halanaerobium enhanced the bioreduction of the chromium during the electrokinetic remediation. This study can be claimed that the microbial cultures assisted electrokinetic remediation of total chromium, organic and iron in the tannery effluent contaminated soil was one of the suitable efficient techniques. In addition, the viability of the new combination technology developed (Electrokinetic + Bio) to treat low-permeability polluted soils was demonstrated.