Molasses as a Whole Medium for Biosurfactants Production by Bacillus Strains and Their Application

A comprehensive review on production of bio-surfactants by bio-degradation of waste carbohydrate feedstocks: an approach towards sustainable development

The advancement of science and technology demands chemistry which is safer, smarter and green by nature. The sustainability of science thus requires well-behaved alternates that best suit the demand. Bio-surfactants are surface active compounds, established to affect surface chemistry. In general, microbial bio-surfactants are a group of structurally diverse molecules produced by different microbes. A large number of bio-surfactants are produced during hydrocarbon degradation by hydrocarbonoclistic microorganisms during their own growth on carbohydrates and the production rate is influenced by the rate of degradation of carbohydrates. The production of such biological surfactants is thus of greater importance. This write up is a dedicated review to update the existing knowledge of inexpensive carbohydrate sources as substrates, microorganisms and technologies of biosurfactant production. This is an economy friendly as well as sustainable approach which will facilitate achieving some sustainable development goals. The production is dependent on the fermentation strategies, different factors of the microbial culture broth and downstream processing; these all have been elaborately presented in this article.

Bioprospecting of the Antarctic Bacillus subtilis strain for potential application in leaching hydrocarbons and trace elements from contaminated environments based on functional and genomic analysis

The production of secondary metabolites including biosurfactants by the Bacillus subtilis ANT_WA51 and the evaluation of its ability to leach metals and petroleum derivatives from the soil, using post-culture medium was investigated. The ANT_WA51 strain isolated from a pristine, harsh Antarctic environment produces the biosurfactants surfactin and fengycin, which reduce the surface tension of molasses-based post-culture medium to 26.6 mN m^-1 at a critical micellization concentration (CMC) of 50 mg L^-1 and a critical micelle dilution (CMD) of 1:19. The presence of biosurfactants and other secondary metabolites in the post-culture medium contributed to significant removal of xenobiotics from contaminated soils in the batch washing experiment - 70% hydrocarbons and 10-23% metals (Zn, Ni and Cu). The isolate's tolerance to different abiotic stresses, including freezing, freeze-thaw cycles, salinity (up to 10%), the presence of metals - Cr(VI), Pb(II), Mn(II), As(V) (up to 10 mM) and Mo(VI) (above 500 mM) and petroleum hydrocarbons (up to 20.000 mg kg^-1) as well as the confirmed metabolic activity of these bacteria in toxic environments in the OxiTop® system indicate that they can be used directly in bioremediation. Comparative genomic analysis of this bacteria revealed a high similarity of its genome to the associated plant strains from America and Europe indicating the wide applicability of plant growth-promoting Bacillus subtilis and that the data can be extrapolated to a wide range of environmental strains. An important aspect of the study was to present the absence of inherent features which would indicate its clear pathogenicity enables its safe use in the environment. Based on the obtained results, we also conclude that the use of post-culture medium, obtained on low-cost byproducts like molasses, for leaching contaminants, especially hydrocarbons, is a promising bioremediation method that can be a replacement for the use of synthetic surfactants and provides a base for further large-scale research but the selection of an appropriate leaching may be dependent on the concentration of contaminants.

Unravelling the sponge microbiome as a promising source of biosurfactants

Microbial surfactants are particularly useful in bioremediation and heavy metal removal from soil and aquatic environments, amongst other highly valued uses in different economic and biomedical sectors. Marine sponge-associated bacteria are well-known producers of bioactive compounds with a wide array of potential applications. However, little progress has been made on investigating biosurfactants produced by these bacteria, especially when compared with other groups of biologically active molecules harnessed from the sponge microbiome. Using a thorough literature search in eight databases, the purpose of the review was to compile the current knowledge on biosurfactants from sponge-associated bacteria, with a focus on their relevant biotechnological applications. From the publications between the years 1995 and 2021, lipopeptides and glycolipids were the most identified chemical classes of biosurfactants. Firmicutes was the dominant phylum of biosurfactant-producing strains, followed by Actinobacteria and Proteobacteria. Bioremediation led as the most promising application field for the studied surface-active molecules in sponge-derived bacteria, despite the reports endorsed their use as antimicrobial and antibiofilm agents. Finally, we appoint some key strategies to instigate the research appetite on the isolation and characterization of novel biosurfactants from the poriferan microbiome.

Enhanced production of biosurfactant by Bacillus subtilis RSL2 in semicontinuous bioreactor utilizing molasses as a sole substrate

The growth-associated metabolites are produced during the exponential phase; however, this phase terminates due to substrate depletion or product inhibition. In the present study, a semicontinuous mode with a fill-and-draw strategy was applied to extend the exponential phase of the biosurfactant production to overcome the product inhibition and in turn, enhance the yield. Bioreactor studies were performed in batch mode, followed by the semicontinuous operation. A potential biosurfactant producer Bacillus subtilis RSL2 was used in this study at the previously optimized conditions of pH 6.6, temperature 41 °C and 5% (w/v) of molasses. A better mass transfer was achieved in the bioreactor as compared to the shake flask study. In the batch bioreactor study, 90% of sugar was utilized with simultaneous 13.7 g L^-1 of biosurfactant production. The sugar utilization was further improved to > 98% in the case of semicontinuous operation employing a fill-and-draw strategy. The exponential phase got extended up to 18 days and a total of 13 L of media was fed in the semicontinuous operation of 21 days as compared to 1.5 L of working volume in the batch reactor. The biosurfactant yield was enhanced by 1.5 folds and was found to be 0.97 g g^-1. The produced biosurfactant was identified as a lipopeptide. The interfacial properties of the biosurfactant along with colloidal and thermal stability have been investigated. The critical micelle concentration of the produced biosurfactant was 70 mg L^-1. The present study highlighted the efficient utilization of molasses for the production of biosurfactant, an alternative metabolite, in a semicontinuous mode of bioreactor.

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.

Bacteria Halotolerant from Karst Sinkholes as a Source of Biosurfactants and Bioemulsifiers

Halotolerant bacteria with biosurfactant (BS) and bioemulsifiers (BE) activity can coexist in Karstic sinkholes with marine influence. Two sinkholes in the Yucatan peninsula were selected to isolate bacteria with BE and BS activity stable in NaCl. The optimal time, the effect of nitrogen and carbon source in the medium, and the conditions (agitation, pH and salinity) for the production of BS and BE compounds in planktonic and sessile (stimulate the formation of biofilms in cell roller) culture were determined. Eighty strains showed the highest emulsification activity (EI24 ≥ 50%) and drop-collapse ≥ 4 mm. 87% of the strains are moderately halotolerant, and 21% bordered the limit of extreme halotolerance. Twenty-four strains maintained or improved their BS and BE activity under salinity conditions at 5% and 10%, being the most active genera Bacillus, Paenibacillus and Lysinibacillus, identified by sequencing of the 16S rRNA gene. The results show that the nitrogen source positively affects the BS and BE activity, regardless of the type of culture. The sessile culture markedly stimulated BS activity with significant differences. However, we did not find a greater influence on the culture conditions. The results suggest that halotolerant bacteria from sinkholes could be implemented in bioremediation and other biotechnological applications.

Lipopeptide Biosurfactants from Bacillus spp.: Types, Production, Biological Activities, and Applications in Food

Biosurfactants are a functionally and structurally heterogeneous group of biomolecules produced by multiple filamentous fungi, yeast, and bacteria, and characterized by their distinct surface and emulsifying ability. The genus Bacillus is well studied for biosurfactant production as it produces various types of lipopeptides, for example, lichenysins, bacillomycin, fengycins, and surfactins. Bacillus lipopeptides possess a broad spectrum of biological activities such as antimicrobial, antitumor, immunosuppressant, and antidiabetic, in addition to their use in skincare. Moreover, Bacillus lipopeptides are also involved in various food products to increase the antimicrobial, surfactant, and emulsification impact. From the previously published articles, it can be concluded that biosurfactants have strong potential to be used in food, healthcare, and agriculture. In this review article, we discuss the versatile functions of lipopeptide Bacillus species with particular emphasis on the biological activities and their applications in food.

Formulation of a Culture Medium to Optimize the Production of Lipopeptide Biosurfactant by a New Isolate of Bacillus sp.: A Soil Heavy Metal Mitigation Approach

This research aimed to optimize a lipopeptide biosurfactant produced from Bacillus sp. SHA302 due to its high efficiency of heavy metal release in soil. The results demonstrated that the metal release capacity of the lipopeptide biosurfactant alone increased with increasing the biosurfactant concentration. Among treatments with different biosurfactant concentrations plus acid, the highest metal release rates of 53.8% ± 1.4 and 39.3% ± 1.7 for Zn and Pb, respectively, were observed in the critical micelle concentration (CMC) + HCl treatment. The results of a factorial experiment designed for optimizing biosurfactant production showed that among five inexpensive carbon sources and six mineral nitrogen sources, sugar beet molasses (1%) and ammonium chloride (0.1%) were the most efficient sources in lowering the surface tension (ST) of the culture media to 32.2 ± 0.76 mN/m. The second step of the experiment was a Plackett-Burman design with 11 factors and showed that the four factors of pH, ammonium chloride, magnesium sulfate, and molasses significantly affected (P < 0.05) the changes in ST and biosurfactant production. The third step of the experiment was done using the response surface methodology (RSM) with a central composite design. The results showed that a pH of 7.3, 1.5 g/l of ammonium chloride, 0.3 g/l of magnesium sulfate, and 10% of sugar beet molasses yielded values of 29.2 ± 0.71 mN/m and 5.74 ± 0.52 g/l for the two variables of ST and biosurfactant production, respectively, which reached their most optimal levels.

Surface properties and heavy metals chelation of lipopeptides biosurfactants produced from date flour by Bacillus subtilis ZNI5: optimized production for application in bioremediation

The present study summarizes the valorization of date flour by the production of lipopeptide biosurfactant (BioS) by Bacillus subtilis ZNI5 (MW091416). A Taguchi design permitted the formulation of a medium composed only of 6% date flour and 0.5% yeast extract within 2 days of incubation at 150 rpm with a maximal surface tension (ST) reduction of about 27.8 mN/m. The characterization of the lipopeptide shows a CMC value of about 400 mg/L with a minimal ST of 30 mN/m and an ability to disperse oil to about 80 mm at 800 mg/L. Having reduced phytotoxicity, the ZNI5 BioS and ZNI5 strain were assayed for Copper and Cobalt chelation and biosorption. The improvement of the germination index of radish seeds irrigated by the treated contaminated water showed the great potential application of ZNI5 lipopeptide in the bioremediation of heavy metals.

A regulated synthetic operon facilitates stable overexpression of multigene terpenoid pathway in Bacillus subtilis

The creation of microbial cell factories for sustainable production of natural products is important for medical and industrial applications. This requires stable expression of biosynthetic pathways in a host organism with favorable fermentation properties such as Bacillus subtilis. The aim of this study is to construct B. subtilis strains that produce valuable terpenoid compounds by overexpressing the innate methylerythritol phosphate (MEP) pathway. A synthetic operon allowing the concerted and regulated expression of multiple genes was developed. Up to 8 genes have been combined in this operon and a stably inherited plasmid-based vector was constructed resulting in a high production of C30 carotenoids. For this, two vectors were examined, one with rolling circle replication and another with theta replication. Theta-replication constructs were clearly superior in structural and segregational stability compared to rolling circle constructs. A strain overexpressing all eight genes of the MEP pathway on a theta-replicating plasmid clearly produced the highest level of carotenoids. The level of transcription for each gene in the operon was similar as RT-qPCR analysis indicated. Hence, that corresponding strain can be used as a stable cell factory for production of terpenoids. This is the first report of merging and stably expressing this large-size operon (eight genes) from a plasmid-based system in B. subtilis enabling high C30 carotenoid production.

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.

Recycling of carbon dioxide by free air CO2 enriched (FACE) Bacillus sp. SS105 for enhanced production and optimization of biosurfactant

Carbon dioxide utilizing bacterium Bacillus sp. SS105 was isolated from FACE (free air CO₂ enriched) sample. The strain was grown in shake flask containing minimal salt medium with 50mM NaHCO₃ as autotrophic carbon source and molasses as a low cost byproduct for mixotrophic growth. Carbon dioxide sequestration property of Bacillus sp. SS105 was determined by enzyme assay of carbonic anhydrase and ribulose-1, 5-bisphosphate carboxylase/oxygenase (RuBisCO). Along with CO₂ sequestration this strain produced biosurfactant and its characterization by FTIR and ¹H NMR indicated lipopeptide nature. Optimization of process parameter along with nutrient sources for higher biosurfactant production was done by Response Surface Methodology (RSM). Under optimized conditions, the yield of biosurfactant and biomass was 2.65 and 2.78gL^-1 respectively. The study revealed simultaneous CO₂ sequestration and biosurfactant production by Bacillus sp. SS105.

Bacillus coagulans MA-13: a promising thermophilic and cellulolytic strain for the production of lactic acid from lignocellulosic hydrolysate

BACKGROUND

The transition from a petroleum-based economy towards more sustainable bioprocesses for the production of fuels and chemicals (circular economy) is necessary to alleviate the impact of anthropic activities on the global ecosystem. Lignocellulosic biomass-derived sugars are suitable alternative feedstocks that can be fermented or biochemically converted to value-added products. An example is lactic acid, which is an essential chemical for the production of polylactic acid, a biodegradable bioplastic. However, lactic acid is still mainly produced by Lactobacillus species via fermentation of starch-containing materials, the use of which competes with the supply of food and feed.

RESULTS

A thermophilic and cellulolytic lactic acid producer was isolated from bean processing waste and was identified as a new strain of Bacillus coagulans, named MA-13. This bacterium fermented lignocellulose-derived sugars to lactic acid at 55 °C and pH 5.5. Moreover, it was found to be a robust strain able to tolerate high concentrations of hydrolysate obtained from wheat straw pre-treated by acid-catalysed (pre-)hydrolysis and steam explosion, especially when cultivated in controlled bioreactor conditions. Indeed, unlike what was observed in microscale cultivations (complete growth inhibition at hydrolysate concentrations above 50%), B. coagulans MA-13 was able to grow and ferment in 95% hydrolysate-containing bioreactor fermentations. This bacterium was also found to secrete soluble thermophilic cellulases, which could be produced at low temperature (37 °C), still retaining an optimal operational activity at 50 °C.

CONCLUSIONS

The above-mentioned features make B. coagulans MA-13 an appealing starting point for future development of a consolidated bioprocess for production of lactic acid from lignocellulosic biomass, after further strain development by genetic and evolutionary engineering. Its optimal temperature and pH of growth match with the operational conditions of fungal enzymes hitherto employed for the depolymerisation of lignocellulosic biomasses to fermentable sugars. Moreover, the robustness of B. coagulans MA-13 is a desirable trait, given the presence of microbial growth inhibitors in the pre-treated biomass hydrolysate.

Optimization of biosurfactant production by Bacillus brevis using response surface methodology

The present study aims to evaluate and validate a statistical model for maximizing biosurfactant productivity by Bacillus brevis using response surface methodology. In this respect, twenty bacterial isolates were screened for biosurfactant production using hemolytic activity, oil spreading technique, and emulsification index (E24). The most potent biosurfactant-producing bacterium (B. brevis) was used for construction of the statistical response surface model. The optimum conditions for biosurfactant production by B. brevis were: 33 °C incubation temperature at pH 8 for 10 days incubation period and 8.5 g/L glucose concentration as a sole carbon source. The produced biosurfactant (BS) (73%) exhibited foaming activity, thermal stability in the range 30–80 °C for 30 min., pH stability, from 4 to 9 and antimicrobial activity against (Escherichia coli). The BS gave a good potential application as an emulsifier.

Application of biosurfactant from Sphingobacterium spiritivorum AS43 in the biodegradation of used lubricating oil

This study aimed at investigating the application of biosurfactant from Sphingobacterium spiritivorum AS43 using molasses as a substrate and fertilizer to enhance the biodegradation of used lubricating oil (ULO). The cell surface hydrophobicity of bacteria, the emulsification activity, and the biodegradation efficiency of ULO were measured. The bacterial adhesion in the hydrocarbon test was used to denote the cell surface hydrophobicity of the used bacterial species. The results indicate a strong correlation between cell surface hydrophobicity, emulsification activity, and the degree of ULO biodegradation. The maximum degradation of ULO (62 %) was observed when either 1.5 % (w/v) of biosurfactant or fertilizer was added. The results also revealed that biosurfactants alone are capable of promoting biodegradation to a large extent without added fertilizer. The data indicate the potential for biosurfactant production by using low-cost substrate for application in the bioremediation of soils contaminated with petroleum hydrocarbons or oils.