UTILIZATION OF SWEETWATER AS A COST-EFFECTIVE CARBON SOURCE FOR SOPHOROLIPIDS PRODUCTION BYStarmerella bombicola(ATCC 22214)

Carbon and nitrogen optimization in solid-state fermentation for sustainable sophorolipid production using industrial waste

The use of alternative feedstocks such as industrial or food waste is being explored for the sustainable production of sophorolipids (SLs). Microbial biosurfactants are mainly produced via submerged fermentation (SmF); however, solid-state fermentation (SSF) seems to be a promising alternative for using solid waste or byproducts that could not be exploited by SmF. Applying the advantages that SSF offers and with the aim of revalorizing industrial organic waste, the impact of carbon and nitrogen sources on the relationship between yeast growth and SL production was analyzed. The laboratory-scale system used winterization oil cake as the solid waste for a hydrophobic carbon source. Pure hydrophilic carbon (glucose) and nitrogen (urea) sources were used in a Box-Behnken statistical design of experiments at different ratios by applying the response surface methodology. Optimal conditions to maximize the production and productivity of diacetylated lactonic C18:1 were a glucose:nitrogen ratio of 181.7:1.43 (w w-1 based on the initial dry matter) at a fermentation time of 100 h, reaching 0.54 total gram of diacetylated lactonic C18:1 with a yield of 0.047 g per gram of initial dry mass. Moreover, time course fermentation under optimized conditions increased the SL crude extract and diacetylated lactonic C8:1 production by 22% and 30%, respectively, when compared to reference conditions. After optimization, industrial wastes were used to substitute pure substrates. Different industrial sludges, OFMSW hydrolysate, and sweet candy industry wastewater provided nitrogen, hydrophilic carbon, and micronutrients, respectively, allowing their use as alternative feedstocks. Sweet candy industry wastewater and cosmetic sludge are potential hydrophilic carbon and nitrogen sources, respectively, for sophorolipid production, achieving yields of approximately 70% when compared to the control group.

Precise fermentation coupling with simultaneous separation strategy enables highly efficient and economical sophorolipids production

Sophorolipids (SLs) represent highly promising biosurfactants. However, its widespread production and application encounter obstacles due to the significant costs involved. Here, an intelligent and precise regulation strategy was elucidated for the fermentation process coupled with in-situ separation production mode, to achieve cost-effective SLs production. Firstly, a mechanism-assisted data-driven model was constructed for "on-demand feeding of cells". Moreover, a strategy of step-wise oxygen supply regulation based on the demand for cell metabolic capacity was developed, which accomplished "on-demand oxygen supply of cells", to optimize the control of energy consumption. Finally, a systematic approach was implemented by integrating a semi-continuous fermentation mode with in-situ separation technology for SLs production. This strategy enhanced SLs productivity and yield, reaching 2.30 g/L/h and 0.57 g/g, respectively. These values represented a 40.2% and 18.7% increase compared to fed-batch fermentation. Moreover, the concentration of crude SLs after separation reached 793.12 g/L, facilitating downstream separation and purification processes.

Harnessing dual applications of a novel ascomycetes yeast, Starmerella cerana sp. nov., as a biocatalyst for stereoselective ketone reduction and biosurfactant production

Introduction: New bioresources for catalytic application and fine chemical synthesis are the need of the hour. In an effort to find out new biocatalyst for oxidation-reduction reaction, leading to the synthesis of chiral intermediates, novel yeast were isolated from unique niche and employed for the synthesis of value added compounds. Methods: To determine the genetic relatedness of the isolated strain, HSB-15T, sequence analysis of the internal transcribed spacer (ITS) and D1/D2 domains of the 26S rRNA gene sequence was carried out. The distinctive features of the strain HSB-15T were also identified by phenotypic characterization. The isolated strain HSB-15T was employed for the reduction of selected naphthyl ketones to their corresponding alcohols and a biosurfactant was isolated from its culture broth. Results: The analysis of the ITS and D1/D2 domains of the 26S rRNA gene revealed that strain HSB-15T is closely related to the type strain of Starmerella vitae (CBS 15147T) with 96.3% and 97.7% sequence similarity, respectively. However, concatenated sequences of the ITS gene and D1/D2 domain showed 94.6% sequence similarity. Phenotypic characterization indicated significant differences between strain HSB-15T and its closely related species and consequently, it was identified as a novel species, leading to the proposal of the name Starmerella cerana sp. nov. The strain was able to reduce selected naphthyl ketones to their corresponding alcohols with remarkable efficiency, within a 12-hours. The strain HSB-15T also produced a surfactant in its culture broth, identified as sophorolipid upon analysis. Discussion: The study explored the potential of the novel strain, HSB-15T, as a whole-cell biocatalyst for the reduction of naphthyl ketones to their corresponding alcohols and also reports its capability to produce sophorolipid, a biosurfactant, in its culture broth. This dual functionality of HSB-15T both as biocatalyst and biosurfactant producer enhances its applicability in biotechnology and environmental science.

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.

Reduced-Cost Production of Sophorolipids by Starmerella bombicola CGMCC1576 Grown on Cottonseed Molasses and Cottonseed Oil-Based Medium

A large-scale application of sophorolipids (SLs) was blocked by their high production cost. One feasible way to reduce the cost of SL production is to develop cheap feedstocks as the substrates for SL fermentation. In the present work, cottonseed molasses (CM), a waste from raffinose production, was used as the hydrophilic substrate;, and cottonseed oil (CO) was used as a hydrophobic substrate for SL production by Starmerella bombicola CGMCC 1576. The primary optimization of carbon sources, nitrogen source and inorganic salts, produced 57.6 ± 2.3 g/L of total SLs and 24.0 ± 1.2 g/L of lactonic SLs on CM and CO, almost equal to the titer of SLs produced from glucose and oleic. A response surface method was applied to optimize the fermentation medium for growth and SL production of S. bombicola. The production of total SLs reached 58.4 ± 3.4 g/L, and lactonic SLs were elevated to more than 25.0 ± 1.9 g/L. HPLC–MS analysis showed that the compositions of SLs produced by S. bombicola on CM and CO were very similar to those on glucose and oleic acid. These results suggested that cottonseed molasses and cottonseed oil can be used as renewable cheap substrates for the reduced-cost production of SLs.

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.

Production of new antimicrobial palm oil-derived sophorolipids by the yeast Starmerella riodocensis sp. nov. against Candida albicans hyphal and biofilm formation

BACKGROUND

Microbial derived-surfactants display low eco-toxicity, diverse functionality, high biodegradability, high specificity, and stability under extreme conditions. Sophorolipids are emerging as key biosurfactants of yeast origins, used in various industrial sectors to lower surface tension. Recently, sophorolipid complexes have been applied in biomedicals and agriculture to eradicate infectious problems related to human and plant fungal pathogens. This study aimed to characterize the functional properties and antifungal activities of sophorolipids produced by a newly characterized Starmerella riodocensis GT-SL1R sp. nov. strain.

RESULTS

Starmerella riodocensis GT-SL1R sp. nov. strain was belonged to Starmerella clade with 93.12% sequence similarity using the ITS technique for strain identification. Sophorolipids production was examined, using co-carbon substrates glucose and palm oil, with a yield on the substrate between 30 and 46%. Using shake-flasks, the S. riodocensis GT-SL1R strain produced biosurfactants with an emulsification activity of 54.59% against kerosene compared to the S. bombicola BCC5426 strain with an activity of 60.22%. Maximum productivities of GT-SL1R and the major sophorolipid-producer S. bombicola were similar at 0.8 gl^-1 h^-1. S. riodocensis GT-SL1R produced mixed forms of lactonic and acidic sophorolipids, shown by TCL, FTIR, and HPLC. Importantly, the complex sophorolipid mixture displayed antifungal activity against an opportunistic yeast pathogen Candida albicans by effectively reducing hyphal and biofilm formation.

CONCLUSIONS

Sophorolipids derived from S. riodocensis demonstrate potential industrial and biomedical applications as green surfactant and antifungal agent. Since numerous renewable bioresources and industrial wastes could be used by microbial cell factories in the biosynthesis of biosurfactants to reduce the production cost, sophorolipids hold a promising alternative to current antimicrobials in treatments against infectious diseases in humans, animals, and plants.

Fermentative Production of Mannosylerythritol Lipids using Sweetwater as Waste Substrate by Pseudozyma antarctica (MTCC 2706)

Mannosylerythritol lipids are glycolipid biosurfactants with promising industrial applications. However, their commercial production is hindered due to its high production cost. The current study investigates the use of sweetwater, a by-product of the fat-splitting industry in combination with soybean oil for the production of mannosylerythritol lipids using Pseudozyma antarctica (MTCC 2706). The optimum sweetwater and soybean oil concentration of 22% and 7% (w/v) yielded 7.52 g L–1and 21.5 g L–1 mannosylerythritol lipids at shake flask and fermenter level respectively. The structure and functional groups of mannosylerythritol lipids were confirmed by fourier transform infrared (FTIR) spectroscopy, liquid chromatography-mass spectrometry (LC/MS) and 1H- and 13C-nuclear magnetic resonance (NMR) analysis. Surfactant properties, such as surface tension, critical micelle concentration, foaming and emulsification of mannosylerythritol lipids were also explored.

Fermentative Production of Sophorolipid and Purification by Adsorption Chromatography

A sophorolipid (glycolipid biosurfactant from Starmerella bombicola) has valuable properties in addition to surface active attributes. This sophorolipid was produced as a secondary metabolite by submerged fermentation using hydrophobic (sunflower oil) and hydrophilic (glucose) substrate. The present work investigates the effect of inoculum age, oil feed and incubation period to increase sophorolipid yield. The highest yield of sophorolipid by sunflower oil was accomplished with an inoculum age of 60 h. Maximum substrate consumption and sophorolipid yield were found near about 200 h. At optimized fermentation conditions, 19.2 g/L yield of sophorolipid was achieved. The lactonic sophorolipid which is the major component of crude sophorolipid was separated and purified by adsorption chromatography. Normal phase and reverse phase resin were compared for adsorptive purification among which reverse phase resin provides better purification with 69 % recovery. Further surfactant and antimicrobial properties of crude sophorolipid were studied.

Biosurfactants produced by Scheffersomyces stipitis cultured in sugarcane bagasse hydrolysate as new green larvicides for the control of Aedes aegypti, a vector of neglected tropical diseases

Biosurfactants are microbial metabolites with possible applications in various industrial sectors that are considered ecofriendly molecules. In recent years, some studies identified these compounds as alternatives for the elimination of vectors of tropical diseases, such as Aedes aegypti. The major bottlenecks of biosurfactant industrial production have been the use of conventional raw materials that increase production costs as well as opportunistic or pathogenic bacteria, which restrict the application of these biomolecules. The present study shows the potential of hemicellulosic sugarcane bagasse hydrolysate as a raw material for the production of a crystalline glycolipidic BS by Scheffersomyces stipitis NRRL Y-7124, which resulted in an emulsifying index (EI24) of 70 ± 3.4% and a superficial tension of 52 ± 2.9 mN.m-1. Additionally, a possible new application of these compounds as biolarvicides, mainly against A. aegypti, was evaluated. At a concentration of 800 mg.L-1, the produced biosurfactant caused destruction to the larval exoskeletons 12 h after application and presented an letal concentration (LC50) of 660 mg.L-1. Thus, a new alternative for biosurfactant production using vegetal biomass as raw material within the concept of biorefineries was proposed, and the potential of the crystalline glycolipidic biosurfactant in larvicidal formulations against neglected tropical disease vectors was demonstrated.

Sophorolipids production from rice straw via SO3 micro-thermal explosion by Wickerhamiella domercqiae var. sophorolipid CGMCC 1576

A novel lignocellulose material, holocellulose from rice straw via the pretreatment of SO3 micro-thermal explosion, was developed to produce sophorolipids (SLs) with Wickerhamiella domercqiae var. sophorolipid CGMCC 1576. The influence factors of inoculum dose, yeast extract concentration and pH regulators (chemical regents used for adjusting/influencing pH) was investigated and discussed. Results showed that W. domercqiae can grow in the rice straw holocellulose hydrolysate, and acquire relative high SL yield of 53.70 ± 2.61 g/L in shake flask culture. Inoculum dose, yeast extract concentration and pH regulator made obvious influence on fermentation parameters, especially on final broth pH and SLs production. Furthermore, there is a strong negative linear correlation existing between final broth pH and lactonic SL or ratio of lac SL/tot SL. Additionally, comparison between SL production and non-glucose carbon sources, culture methods, microbes in previous reports was carried out. These results will be benefit for acquiring SL mixture with suitable lac SL/tot SL ratio for specific purpose and scope economically.

Sophorolipids Production by Candida bombicola ATCC 22214 and its Potential Application in Microbial Enhanced Oil Recovery

Biosurfactant production using Candida bombicola ATCC 22214, its characterization and potential applications in enhancing oil recovery were studied at laboratory scale. The seed media and the production media were standardized for optimal growth and biosurfactant production. The production media were tested with different carbon sources: glucose (2%w/v) and corn oil (10%v/v) added separately or concurrently. The samples were collected at 24 h interval up to 120 h and checked for growth (OD660), and biosurfactant production [surface tension (ST) and interfacial tension (IFT)]. The medium with both glucose and corn oil gave better biosurfactant production and reduced both ST and IFT to 28.56 + 0.42mN/m and 2.13 + 0.09mN/m, respectively within 72 h. The produced biosurfactant was quite stable at 13-15% salinity, pH range of 2-12, and at temperature up to 100°C. It also produced stable emulsions (%E24) with different hydrocarbons (pentane, hexane, heptane, tridecane, tetradecane, hexadecane, 1-methylnaphthalene, 2,2,4,4,6,8-heptamethylnonane, light and heavy crude oil). The produced biosurfactant was extracted using ethyl acetate and characterized as a mixture of sophorolipids (SPLs). The potential of SPLs in enhancing oil recovery was tested using core-flooding experiments under reservoir conditions, where additional 27.27% of residual oil (Sor) was recovered. This confirmed the potential of SPLs for applications in microbial enhanced oil recovery.

Sophorolipids Synthesized Using Non-Traditional Oils with Glycerol and Studies on Their Surfactant Properties with Synthetic Surfactant

The importances of bio-surfactants in industrial applications are huge due to their biodegradable and eco-friendly nature. Bio-surfactants mostly find application in cosmetics and health care products. Moreover, bio-surfactants like sophorolipids (SL) also exhibit antimicrobial and skin healing properties. The current studies involve production of SL using low cost substrates like glycerol (15%) instead of glucose (10%) with non-traditional oils (10%) such as jatropha oil, karanja oil and neem oil by using Starmerella bombicola (ATCC 22214). Neem oil gave lower yield i.e. (1.42 g/L) of SL as compared to jatropha oil (4.74 g/L) and karanja oil (5.91 g/L) with glycerol as substrate. Some pretreatment given to crude neem oil like oil refining and ethanol washing with glycerol helps in improved cell growth and SL yield i.e. 2.73 g/L and 3.82 g/L respectively. The comparison thin layer chromatography (TLC), Fourier Transform infrared spectra (FTIR), high performance liquid chromatography (HPLC), liquid chromatography mass spectra (LC-MS) and proton nuclear magnetic resonance spectroscopy (1H NMR) of SL produced on non-traditional oils with glycerol were carried out with that of SL produced on non-traditional oils with glucose. The surfactant properties of sodium lauryl sulphate (SLS) such as surface tension, interfacial tension, stabilization of foam, emulsification, and wetting were improved when SLS was replaced at different concentration of SL.