Evaluation of a new strategy in the elaboration of culture media to produce surfactin from hemicellulosic corncob liquor

Use of corncob and pineapple peel as associated substrates for biosurfactant production

Biosurfactants are amphiphilic biomolecules with promising tensoative and emulsifying properties that find application in the most varied industrial sectors: environment, food, agriculture, petroleum, cosmetics, and hygiene. In the current work, a 23 full-factorial design was performed to evaluate the effect and interactions of pineapple peel and corncob as substrates for biosurfactant production by Bacillus subtilis LMA-ICF-PC 001. In a previous stage, an alkaline pretreatment was applied to corncob samples to extract the xylose-rich hydrolysate. The results indicated that pineapple peel extract and xylose-rich hydrolysate acted as partial glucose substitutes, minimizing production costs with exogenous substrates. Biosurfactant I (obtained at 8.11% pineapple peel extract, 8.11% xylose-rich hydrolysate from corncob, and 2.8109 g/L glucose) exhibited a significant surface tension reduction (52.37%) and a promising bioremediation potential (87.36%). On the other hand, biosurfactant III (obtained at 8.11% pineapple peel extract, 31.89% xylose-rich hydrolysate from corncob, and 2.8109 g/L glucose) exhibited the maximum emulsification index in engine oil (69.60%), the lowest critical micellar concentration (68 mg/L), and the highest biosurfactant production (5.59 g/L). These findings demonstrated that using pineapple peel extract and xylose-rich hydrolysate from corncob effectively supports biosurfactant synthesis by B. subtilis, reinforcing how agro-industrial wastes can substitute traditional carbon sources, contributing to cost reduction and environmental sustainability.

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.

Available strategies for improving the biosynthesis of surfactin: a review

Surfactin is an excellent biosurfactant with a wide range of application prospects in many industrial fields. However, its low productivity and high cost have largely limited its commercial applications. In this review, the pathways for surfactin synthesis in Bacillus strains are summarized and discussed. Further, the latest strategies for improving surfactin production, including: medium optimization, genome engineering methods (rational genetic engineering, genome reduction, and genome shuffling), heterologous synthesis, and the use of synthetic biology combined with metabolic engineering approaches to construct high-quality artificial cells for surfactin production using xylose, are described. Finally, the prospects for improving surfactin synthesis are discussed in detail.

Evaluation of Biosurfactant Production by Bacillus Species Using Glucose and Xylose as Carbon Sources

Lignocellulosic material is one of the raw materials that can be used to reduce the cost of biosurfactant production because it is cheap, abundantly available, and contains cellulose and hemicellulose which can be hydrolyzed to glucose and xylose as carbon sources. This study aimed to evaluate biosurfactant production by Bacillus species using glucose and xylose as carbon sources, which are the most abundant sugar monomers from the hydrolysis of lignocellulosic materials. In this study, biosurfactants were produced by six bacterial isolates belonging to the Bacillus genus. The six bacterial isolates were identified molecularly through 16S rRNA sequencing. The results showed that the six bacterial isolates were identified as B. subtilis ITBCC46, B. subtilis ITBCC40, B. subtilis ITBCC31, B. siamensis ITBCC36, B. xiamenensis ITBCC43, and B. subtilis ITBCC30. All Bacillus species used in this study could be grown on glucose or xylose media. Biosurfactants produced by B. subtilis ITBCC46, B. subtilis ITBCC40, B. subtilis ITBCC31, and B. siamensis ITBCC36 could reduce surface tension below 40 mN/m (32.70 to 39.15 mN/m). All biosurfactants produced by these Bacillus species had more than 50% emulsification stability. These characteristics indicated that the biosurfactants had the desired quality.

Bacillus-Loaded Biochar as Soil Amendment for Improved Germination of Maize Seeds

Biochar is considered one of the most promising long-term solutions for soil quality improvement, representing an ideal environment for microorganisms' immobilization. Hence there is a possibility to design microbial products formulated using biochar as a solid carrier. The present study was aimed at development and characterization of Bacillus-loaded biochar to be applied as a soil amendment. The producing microorganism Bacillus sp. BioSol021 was evaluated in terms of plant growth promotion traits, indicating significant potential for production of hydrolytic enzymes, indole acetic acid (IAA) and surfactin and positive tests for ammonia and 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase production. Soybean biochar was characterised in terms of physicochemical properties to evaluate its suitability for agricultural applications. The experimental plan for Bacillus sp. BioSol021 immobilisation to biochar included variation of biochar concentration in cultivation broth and adhesion time, while the soil amendment effectiveness was evaluated during maize germination. The best results in terms of maize seed germination and seedling growth promotion were achieved by applying 5% of biochar during the 48 h immobilisation procedure. Germination percentage, root and shoot length and seed vigour index were significantly improved when using Bacillus-biochar soil amendment compared to separate treatments including biochar and Bacillus sp. BioSol021 cultivation broth. The results indicated the synergistic effect of producing microorganism and biochar on maize seed germination and seedling growth promotion, pointing out the promising potential of this proposed multi-beneficial solution for application in agricultural practices.

Genetic engineering of the branched-chain fatty acid biosynthesis pathway to enhance surfactin production from Bacillus subtilis

Surfactin, which is composed of a β-hydroxy fatty acid chain and a peptide ring, has drawn considerable attention due to its potential applications in the biomedicine, bioremediation, and petroleum industries. However, the low yield of surfactin from wild strains still restricts its industrial applications. In this study, eight genes relevant to the fatty acid biosynthesis pathway were targeted to enhance surfactin production, and high surfactin-yielding strains with potential industrial applications were obtained. When ldeHA and acc were co-overexpressed, the surfactin yield of recombinant strains TDS8 and TPS8 increased to 1.55- and 1.19-fold of their parental strains, respectively, again proving that the conversion of acetyl-coenzyme A (CoA) to malonyl-CoA is the rate-limiting step in fatty acid biosynthesis. Furthermore, changes in surfactin isoforms of recombinant strain TPS8 suggest that the fatty acid precursor synthesis pathway can be modified to improve the proportion of different isoforms. In addition, the deletion of lpdV, which is responsible for the conversion of α-ketoacyl-CoA precursors, resulted in a sharp decrease in surfactin production, further demonstrating the importance of branched-chain fatty acid biosynthesis in surfactin production. This work will facilitate the design and construction of more efficiently engineered strains for surfactin production and further extend industrial applications.

Biosurfactant Production from Pineapple Waste and Application of Experimental Design and Statistical Analysis

The use of non-conventional carbon sources for biosurfactant-producing microorganisms is a promising alternative in fermentation to substitute costly substrates. So, the current research used pineapple peel as a cost-effective and renewable substrate because of its rich composition in minerals and sugars and high availability. Following a 2² full factorial design, a bacterial strain of Bacillus subtilis produced biosurfactants in fermentative media containing different concentrations of glucose and concentrated pineapple peel juice (CPPJ). The influence of these two independent variables was evaluated according to three different responses: surface tension reduction rate (STRR), emulsification index (EI₂₄), and concentration of semi-purified biosurfactant (SPB). The maximum value for STRR (57.63%) was obtained in media containing 0.58% glucose (w/v) and 5.82% CPPJ (v/v), while the highest EI₂₄ response (58.60%) was observed at 2% glucose (w/v) and 20% CPPJ (v/v) and maximum SPB (1.28 g/L) at 3.42% glucose (w/v) and 34.18% CPPJ (v/v). Statistical analysis indicated that the CPPJ variable mostly influenced the STRR and SPB responses, whereas the EI₂₄ was significantly influenced by pineapple peel juice and glucose contents.

Modeling biosurfactant production from agroindustrial residues by neural networks and polynomial models adjusted by particle swarm optimization

Biosurfactants are molecules with wide application in several industrial processes. Their production is damaged due to inefficient bioprocessing and expensive substrates. The latest developments of strategies to improve and economize the biosurfactant production process use alternative substrates, optimization techniques, and different scales. This paper presents a study to compare the performances of classical (polynomial models) and modern tools, such as artificial intelligence to aid optimization of the alternative substrate concentration (alternative based on beet peel and glycerol) and process parameters (agitation and aeration). The evaluation was developed in two different scales: Erlenmeyer flask (100 mL) and bioreactor (7 L). The intelligent models were implemented to verify the ability to predict the emulsification index and biosurfactant concentration in smaller scale and the biosurfactant concentration and the superficial tension reduction (STR) in bigger scale, resulting in four different situations. The overall results of the predictions led to artificial neural networks as the best performing modeling tool in all four situations studied, with R² values ranging from 0.9609 to 0.9974 and error indices close to 0. Also, four different models (Wu, Contois, Megee, and Ghose-Tyagi) were adjusted by particle swarm optimization (PSO) in order to describe the kinetics of biosurfactant production. Contois model was the only one to present R² ≥ 0.97 for all monitored variables. The findings described in this work present an adjusted model for the prediction of biosurfactant production and also state that the most adjusted kinetic model for further studies on this process is Contois model, leading to the conclusion that biomass growth is limited by a single substrate, considering only glucose.

Potential of pineapple peel in the alternative composition of culture media for biosurfactant production

The large pineapple's consumption and processing have generated a massive amount of waste yearly, which requires adequate treatment measures to avoid damages to the environment. Pineapple peel is one of the main residues obtained from this fruit and a promising strategy to take advantage of its potential is using it for biosurfactant production due to the peel's rich composition in fermentable sugars and nutrients, such as potassium and magnesium that favor the Bacillus subtilis growth and biosurfactant excretion as well. The current research performed a central composite design (CCD) with four independent variables (glucose, pineapple peel, potassium, and magnesium), evaluating substrates' influence on the surface tension reduction rate (STRR) and the emulsification index (EI₂₄). The results indicated that pineapple peel has the necessary potential to act as a partial substitute for glucose and salt nutrients, minimizing the costs of supplementing with exogenous minerals. The highest surface tension reduction rate (57.744%) was obtained at 2.18% glucose (w/v); 14.67% pineapple peel (v/v); 2.38 g/L KH₂PO₄; and 0.15 g/L MgSO₄.7H₂O; whereas to obtain the maximum predicted value for EI₂₄ (61.92%) the medium was composed by 2.24% glucose (w/v); 12.63% pineapple peel (v/v); 2.53 g/L KH₂PO₄; and 0.29 g/L MgSO₄.7H₂O.

Exploiting Microbes in the Petroleum Field: Analyzing the Credibility of Microbial Enhanced Oil Recovery (MEOR)

Crude oil is a major energy source that is exploited globally to achieve economic growth. To meet the growing demands for oil, in an environment of stringent environmental regulations and economic and technical pressure, industries have been required to develop novel oil salvaging techniques. The remaining ~70% of the world’s conventional oil (one-third of the available total petroleum) is trapped in depleted and marginal reservoirs, and could thus be potentially recovered and used. The only means of extracting this oil is via microbial enhanced oil recovery (MEOR). This tertiary oil recovery method employs indigenous microorganisms and their metabolic products to enhance oil mobilization. Although a significant amount of research has been undertaken on MEOR, the absence of convincing evidence has contributed to the petroleum industry’s low interest, as evidenced by the issuance of 400+ patents on MEOR that have not been accepted by this sector. The majority of the world’s MEOR field trials are briefly described in this review. However, the presented research fails to provide valid verification that the microbial system has the potential to address the identified constraints. Rather than promising certainty, MEOR will persist as an unverified concept unless further research and investigations are carried out.

Biosurfactants produced from corncob: a bibliometric perspective of a renewable and promising substrate

The reuse of agro-industrial waste has been a recurring issue since the 20th century. With a composition rich in carbohydrates and because of the massive amount of residue produced daily all over the world, corncob became a low-cost and suitable substrate to produce high added-value compounds. Biosurfactants are bioproducts of versatile applications due to their chemical structure with hydrophilic and hydrophobic regions. The current work performed a bibliometric analysis to identify research related to the synthesis of biosurfactants using corncob as substrate. Despite the high availability of corncobs, only nine articles were found in Scopus and Web of Science using different pretreatment processes and microorganisms. After an initial screening, data regarding research organizations, scientific journals, citations, countries, institutions, and keywords were analyzed. Results indicated that corncobs were also used to produce enzymes, adsorbents, activated carbon, and furfural. The presented evaluation updated the status of art, identifying a serious need for more research, especially because of corncob's high potential to provide fermentable sugars and the wide range of variables influencing fermentation processes that still need to be studied. A future association of this low-cost substrate with other methods can result in a promising scenario for technology transference.

Biosurfactant inducers for enhanced production of surfactin and rhamnolipids: an overview

Biosurfactants can be widely used in industries as pharmaceutical agents, for microbial enhanced oil recovery, crop biostimulation, among others. Surfactin and rhamnolipids are well-known biosurfactants. These compounds have several advantages over chemical surfactants, however they are not economically competitive, since their production cost is up to 12 times higher than chemical surfactants. In this sense, an interesting approach is to replace synthetic culture medium, which represents ≈ 30% of the production cost by agro-industrial wastes. In addition, biosurfactant productivity can be easily enhanced by inductor supplementation into culture medium that triggers biosurfactant metabolism. Biosurfactant inducers are mainly a pool of hydrophobic molecules (e.g. olive oil-saturated and unsaturated fatty acids, proteins and vitamins). Nevertheless, there is little information on inducer effects of specific molecules (e.g. oleic acid). In general, hydrophobic inducers lead to higher fatty acid chain lengths (biosurfactant chemical structure). Therefore, the aim of this review was to critically discuss the current state of the art and future trends on biosurfactant production, in particular biosurfactant inducers. Taking into account the last 10 years, there is a clear lack of information on correlation between "inducers" or "hydrophobic inducers" AND "biosurfactants", since only 13 documents were found (Scopus database). Thus, it is essential to deeply investigate all inducer effects on biosurfactant production, mainly yield and chemical structure.

Exploring Antifouling Activity of Biosurfactants Producing Marine Bacteria Isolated from Gulf of California

Biofouling causes major problems and economic losses to marine and shipping industries. In the search for new antifouling agents, marine bacteria with biosurfactants production capability can be an excellent option, due to the amphipathic surface-active characteristic that confers antimicrobial and antibiofilm activities. The aim of this study was to evaluate the antifouling activity of biosurfactants producing marine bacteria from the Gulf of California. The cell free culture supernatant (CFCS) of Bacillus niabensis (S-69), Ralstonia sp. (S-74) (isolated from marine sediment) and of B. niabensis (My-30) (bacteria associated to the sponge Mycale ramulosa) were screened for production of biosurfactants (using hemolysis and drop collapse test, oil displacement and emulsifying activity). The toxicity and antifouling activity were evaluated against biofoulers (bacteria forming biofilm and macrofoulers) both in laboratory and field assays. The results indicate that all bacteria were biosurfactant producers, but the higher capability was shown by B. niabensis (My-30) with high emulsifying properties (E24) of 71%. The CFCS showed moderate toxicity but were considered non-toxic against Artemia franciscana at low concentrations. In the antifouling assay, the CFCS of both strains of B. niabensis showed the best results for the reduction of the biofilm formation (up 50%) against all Gram-positive bacteria and most Gram-negative bacteria with low concentrations. In the field assay, the CFCS of B. niabensis (My-30) led to the reduction of 30% of biofouling compared to the control. The results indicate that the biosurfactant produced by B. niabensis (My-30) has promising antifouling activity.