Corn Steep Liquor Research Articles

Investigating the concomitant production of carotenoids and lipids by the yeast Rhodosporidium babjevae using sugarcane bagasse hydrolysate or corn steep liquor

Investigating the concomitant production of carotenoids and lipids by the yeast Rhodosporidium babjevae using sugarcane bagasse hydrolysate or corn steep liquor

A non-aseptic bioprocess for production and recovery of 2,3-butanediol via conversion of crude glycerol and corn steep liquor at pilot-scale

The production and recovery of 2,3-butanediol (BDO) through biodiesel derived glycerol valorization by Klebsiella oxytoca ACA-DC 1581 was holistically optimized with regard to the efficiency and cost of the bioprocess. The absence of thermal treatment of the substrate had no negative effect upon the growth of microorganism and the bioconversion of crude glycerol into BDO, enabling the development of a non-aseptic and lower-cost bioprocess. Both digestate and corn steep liquor (CSL), the main by-products of the biogas and corn industries respectively, successfully served as the sole source of nitrogen, contributing to the complete replacement of more expensive sources (e.g., yeast extract). The biochemical pathway of glycerol catabolism was examined under varying concentrations of dissolved oxygen and BDO production was optimized in a fully aerobic environment (volumetric mass transfer coefficient; kLa = 70.5 1/h.) The glycerol consumption rate was 2.80 g/L/h, the BDO productivity reached 1.12 g/L/h and the yield of BDO produced per unit of glycerol consumed was 0.46 g/g, with these values being among the highest ones reported in the literature for wild-type strains cultivated on crude glycerol. In all fed-batch fermentations, final BDO and acetoin concentration reached ∼80 g/L, while a plateau was observed at ∼68 g/L of BDO. Finally, the culture was carried out efficiently in the pilot-scale reactor (250 L). The salting-out extraction (SOE), consisting of ethanol (24 %) and K2HPO4 (25 %), recovered 91.7 % of BDO from the fermentation medium and was studied for the first time in a glycerol-based medium. The study suggests the potential industrialization of the bioprocess through sustainable, pilot-scale and low-cost bioconversion of biodiesel-derived crude glycerol and CSL or digestate into BDO.

Evaluating Organic Fertilizers and Microbial Inoculation for Soilless and Hydroponic Crop Production

Because hydroponic operations in the United States can be certified as organic, and because the price of chemical fertilizers has increased, there is an increasing interest in using organic fertilizers and beneficial microorganisms for controlled-environment agriculture. However, there is a scarcity of information regarding their effectiveness and application methodologies. We investigated the effects of inoculating Azospirillum brasilense and Rhizophagus intraradices and using organic fertilizers on growing lettuce (Lactuca sativa ‘Cherokee’) and tomato (Solanum lycopersicum ‘Red Robin’) young plants in an indoor vertical farm. Seeds were sown in rockwool substrate, with A. brasilense (1.05 × 108 colony-forming units⋅L−1) or R. intraradices (580 propagules⋅L−1) applied weekly via subirrigation. Seedlings received chemical fertilizer, organic fertilizer derived from corn steep liquor and fermented fish by-products, and food waste-derived organic fertilizer at 100 ppm total nitrogen every 2 or 3 days. They were grown indoors at 23 °C under light-emitting diode lighting at a photosynthetic photon flux density of 200 μmol⋅m−2⋅s−1 with an 18-hour photoperiod. Lettuce under organic fertilizers had 75% lower shoot fresh mass and 64% less shoot dry mass compared with lettuce under chemical fertilizer. Similarly, tomato seedlings with organic fertilizers had fewer leaves, 75% less shoot fresh mass, and 67% less shoot dry mass. In both lettuce and tomato, the macronutrient and micronutrient concentrations in plant tissues were generally similar regardless of fertilizer treatments, but nitrogen use efficiency and nitrogen uptake efficiency were lower under organic fertilizers compared with those under chemical fertilizer. The inoculation of A. brasilense or R. intraradices showed limited effects on plant nutrient uptake, nutrient concentrations, and seedling growth in both lettuce and tomato. Further research is necessary to optimize application methods for organic fertilizers and beneficial microorganisms to fully harness the benefits of sustainable alternative fertilizers in soilless and hydroponic crop production.

Use of Corn Steep Liquor as a Biostimulant in Agriculture

Biostimulants are substances or microorganisms that are applied to plants, soil, or seeds, to improve the growth, development, performance, and quality of crops. Their application is mainly directed towards improving the resistance of crops against abiotic and biotic stresses. These compounds are formulated from a great variety of compounds: humic substances, complex organic materials (sewage sludge extracts, composts, and manure), chemical elements (Al, Co, Na, Se, and Si), inorganic salts including phosphite, seaweed extracts (brown, red, and green), amino acids, etc. As of today, it has been observed that corn steep liquor (CSL), which is obtained from the industrial process of corn transformation, may be a good ingredient for the formulation of biostimulant products. CSL contains a large amount of different chemical compounds with biological activity for the plants and soil. The use of CSL industrial waste, previously formulated, could have a direct or indirect effect on the physiological processes and metabolic routes of plants related to the adaptation to abiotic and biotic stresses, as their compounds are part of these metabolic pathways, act as elicitor compounds, and/or have their own biological activity in the plants. There is evidence that the application of CSL could protect plants from specific abiotic and biotic stresses, such as an excess of light or temperature, nutritional limitations, salinity, drought, or pathogens. In addition, it can improve the growth of the plant when these are grown in hydroponic systems, and can improve the health of soils. The present article is focused on describing the most relevant scientific aspects of CSL when used as an ingredient to formulate biostimulants for agriculture. It will discuss its chemical composition, the analytical techniques utilized to elucidate and quantify its compounds, its uses in agriculture, and mode of action in the plants.

An Evaluation of the Effectivity of the Green Leaves Biostimulant on Lettuce Growth, Nutritional Quality, and Mineral Element Efficiencies under Optimal Growth Conditions.

The use of biostimulants is becoming a useful tool for increasing crop productivity while enhancing nutritional quality. However, new studies are necessary to confirm that the joint application of different types of biostimulants, together with bioactive compounds, is effective and not harmful to plants. This study examined the impact of applying the biostimulant Green Leaves, comprising Macrocystis algae extract and containing a mixture of amino acids, corn steep liquor extract, calcium, and the bioactive compound glycine betaine. The effect of applying two different doses (3 and 5 mL L-1) of this biostimulant was evaluated on lettuce plants, and growth and quality parameters were analyzed along with photosynthetic efficiency, nutritional status, and nutrient efficiency parameters. The application of Green Leaves improved plant weight (25%) and leaf area and enhanced the photosynthetic rate, the accumulation of soluble sugars and proteins, and the agronomic efficiency of all essential nutrients. The 3 mL L-1 dose improved the nutritional quality of lettuce plants, improving the concentration of phenolic compounds and ascorbate and the antioxidant capacity and reducing NO3- accumulation. The 5 mL L-1 dose improved the absorption of most nutrients, especially N, which reduced the need for fertilizers, thus reducing costs and environmental impact. In short, the Green Leaves product has been identified as a useful product for obtaining higher yield and better quality.

Spray drying of cellulases produced by Bacillus sp. SMIA-2

Microbial cellulases present biotechnological potential to be used in several industries, including food, brewery and wine, industrial waste for chemical feedstock, animal feed, pulp and paper, agriculture, textile and detergent production. In this work, cellulases produced by the thermophilic Bacillus sp. SMIA-2 in submerged cultures containing sugarcane bagasse, corn steep liquor and passion fruit rind flour were spray-dried, in an attempt to improve their stability for industrial purposes. The cellulases were spray dried and analyzed before and after the drying process and subsequent storage. A Central Composite Design (CCD) 23 was used to investigate the effect of different concentrations of arabic gum and microcrystalline cellulose, as well as the spray dryer inlet temperature on the cellulase spray drying process. The results evidenced that the combination of 1.0 % (w/v) arabic gum and 1.0% (w/v) microcrystalline cellulose, at inlet temperature of 70 °C, was effective in maintaining the activities of both avicelases (avicel-hydrolyzing enzymes) and carboxymethylcellulases (carboxymethylcellulose-hydrolyzing enzymes - CMCase). The dried avicelase was completely preserved when stored at 5oC, while the CMCase retained 89% of its activity, which indicates promising potential for industrial uses, especially in detergent formulations.

Monitoring Yeast Cultures Grown on Corn Stover Hydrolysate for Lipid Production

Microbial oils can be used as an alternative sustainable and renewable feedstock to fossil reserves for producing lubricants and polyurethane materials. Two oleaginous yeasts were grown on non-detoxified corn stover hydrolysate supplemented with corn steep liquor and mineral medium in shake flasks. Trichosporon oleaginosus DSM 11815 displayed the highest lipid production. This strain was further cultivated in a bench bioreactor, using the same culture medium, under a batch regime. Flow cytometry was used to monitor the T. oleaginosus culture using the dual staining technique (SYBR Green and PI) for cell membrane integrity detection. Values of 42.28% (w/w) and 0.06 g/Lh lipid content and lipid productivity, respectively, were recorded for T. oleaginosus cultivated in the bench bioreactor operated under a batch regime. During the cultivation, most of the yeast cells maintained their integrity. T. oleaginosus has the potential to be used as an oil microbial source for a wide range of industrial applications. In addition, it is robust in adverse conditions such as lignocellulosic hydrolysate exposure and oxygen-limiting conditions. Flow cytometry is a powerful and useful tool for monitoring yeast cultivations on lignocellulosic hydrolysates for cell count, size, granularity, and membrane integrity detection.

Improved Cordycepin Production by Cordyceps Militaris Using Corn Steep Liquor Hydrolysate as an Alternative Protein Nitrogen Source.

Cordycepin production in the submerged culture of Cordyceps militaris was demonstrated using hydrolyzed corn processing protein by-products, known as corn steep liquor hydrolysate (CSLH), as an alternative nitrogen source. The growth, metabolism, and cordycepin production of Cordyceps militaris were evaluated under various concentrations of CSLH induction. The results demonstrated that CSLH addition had positive effects on the growth and cordycepin production with various C. militaris strains. The optimum strain, C. militaris GDMCC5.270, was found to effectively utilize CSLH to promote mycelium growth and cordycepin production. Low concentrations of CSLH (1.5 g/L) in the fermentation broth resulted in 343.03 ± 15.94 mg/L cordycepin production, which was 4.83 times higher than that of the group without CSLH. This also enhanced the metabolism of sugar, amino acids, and nucleotides, leading to improved cordycepin biosynthesis. The increase in key amino acids, such as glutamic acid, alanine, and aspartic acid, in the corn steep liquor hydrolysate significantly enhanced cordycepin yield. The corn steep liquor hydrolysate was confirmed to be a cost-effective accelerator for mycelium growth and cordycepin accumulation in C. militaris, replacing partial peptone as a cheap nitrogen source. It serves as a suitable alternative for efficient cordycepin production at a low cost.

Uncovering the mechanisms of how corn steep liquor and microbial communities minimize cadmium translocation in Chinese cabbage.

Corn steep liquor-assisted microbial remediation has been proposed as a promising strategy to remediate cadmium (Cd)-contaminated soil. In this study, we determined Bacillus subtilis (K2) with a high cadmium (Cd) accumulation ability and Cd resistance. However, studies on this strategy used in the Cd uptake of Chinese cabbage are lacking, and the effect of the combined incorporation of corn steep liquor and K2 on the functions and microbial interactions of soil microbiomes is unclear. Here, we study the Cd uptake and transportation in Chinese cabbage by the combination of K2 and corn steep liquor (K2 + C7) in a Cd-contaminated soil and corresponding microbial regulation mechanisms. Results showed that compared to inoculant K2 treatment alone, a reduction of Cd concentration in the shoots by 14.4% and the dry weight biomass of the shoots and the roots in Chinese cabbage increased by 21.6% and 30.8%, respectively, under K2 + C7 treatment. Meanwhile, hydrogen peroxide (H2O2) and malondialdehyde (MDA) levels were decreased by enhancing POD and SOD activity, thereby reversing Cd-induced oxidative damage. Importantly, inoculation of K2 would decrease the diversity of the microbial community while enhancing the abundance of dominant species. These findings provide a promising strategy for reducing the Cd accumulation in Chinese cabbage and recovering soil ecological functions.

Evaluation of antimicrobial effect of bacteriocin produced by Lactobacillus acidophilus utilizing molasses and corn steep liquor

Bacteriocins are antimicrobial peptides produced by lactic acid bacteria (LAB) which have emerged as safe bio-preservatives in the food industry. However, the conventional commercial medium used to promote bacteriocin production is often costly and impractical for industrial-scale production. This study aimed to explore the utilization of industrial by-products, specifically molasses and corn steep liquor (CSL), in fermentation medium for producing bacteriocin from Lactobacillus acidophilus. The produced bacteriocin was subsequently formulated into antimicrobial powder, and their inhibitory effects on two common foodborne pathogens, Escherichia coli O157 and Salmonella sp. S251, were examined. Among the various medium compositions tested, the highest percentage of inhibition against E. coli 0157 and Salmonella sp. S251 were achieved in the medium containing 10% (v/v) of molasses and 4% (v/v) of CSL. In the formulation of bacteriocin powder, the addition of 60% (w/v) of starch, combined with silicon dioxide, resulted in the shortest drying time. Moreover, the bacteriocin powder produced from 4-fold concentrated bacteriocin at a concentration of 10% (w/v) led to the highest antimicrobial activity against both pathogenic bacteria. Therefore, the efficient production of bacteriocin with remarkable inhibitory effects on foodborne pathogens from L. acidophilus is feasible by utilizing nutrient-rich and cost-effective molasses and CSL.

Corn Steep Liquor application on pepper plants (Capsicum annum L.) stimulates growth under nitrogen-deficient growing conditions

Excessive nitrogen fertilization in crops is causing serious environmental problems related to eutrophication of natural resources such as seas, aquifers, coastal lagoons like the Mar Menor (Spain), etc. Therefore, there is a need to design agronomic strategies that allow plants to be grown below their nutritional requirements, primarily nitrogen. One of these strategies is the use of biostimulants products made from botanical extracts, as they contain active compounds that stimulate certain metabolic processes in plants favoring nitrogen absorption and assimilation. In this experiment, foliar and root application of Corn Steep Liquor (CSL) extract was evaluated at four stages of pepper plant (Capsicum annuum L.) cultivation under different amounts of nitrogen, ranging from 100 % to 25% N. At the end of the experiment parameters of vegetative growth, nitrate, ammonium, total nitrogen concentration in the leaves, amino acid concentration, soluble proteins, and the enzymatic activities of glutamine synthetase and nitrate reductase were measured. The results showed that plants reduced their vegetative growth as nitrogen concentration in the nutrient solution decreased. However, this reduction was less pronounced in plants treated with exogenous CSL in the leaves, improving the efficient use of nitrogen (NUtE and NUE in particular) by increasing nitrogen assimilation (NR and GS enzymatic activities) and the concentration of amino acids and proteins.

Using Omics Techniques to Analyze the Effects of Gene Mutations and Culture Conditions on the Synthesis of β-Carotene in Pantoea dispersa

β-carotene possesses antioxidant properties and holds significant research value. In our study, we have successfully identified a strain of Pantoea dispersa MSC14 which has the capability to produce β-carotene. By incorporating corn steep liquor powder into culture medium and employing mutagenesis breeding techniques, we have successfully increased the production of β-carotene in the MSC14 strain by 13.97% and 29.22%, respectively. To gain further insights, we conducted genomic and transcriptomics analyses. These analyses revealed a significant mutation in the gndA (6-phosphogluconate dehydrogenase) gene of the mutant strain 14P9, resulting in a 33.74% decrease in 6-phosphogluconate dehydrogenase activity. Using transcriptomics analysis, we investigated the impact of this mutation on β-carotene production and explored the interconnectedness between carbon metabolism, fatty acid metabolism, amino acid metabolism, and β-carotene synthesis. The up-regulation of the trxC (Thioredoxin-2) gene, as observed in both transcriptomics results, prompted us to construct strains that overexpress trxC. This manipulation resulted in a notable 15.89% increase in β-carotene production, highlighting the significant impact of of the trxC gene on the β-carotene content of Pantoea dispersa. In conclusion, our study has successfully identified Pantoea dispersa MSC14 as a proficient producer of β-carotene. Furthermore, we have uncovered two genes implicated in the biosynthesis of β-carotene. These findings enhance our understanding of β-carotene synthesis and provide valuable guidance for carotenoid biosynthesis.

Integrated Microbiome and Metabolomics Analysis of the Effects of Dietary Supplementation with Corn-Steep-Liquor-Derived Candida utilis Feed on Black Pigs.

In this experiment, glucose master liquor and corn steep liquor were used as carbon and nitrogen sources, and Candida utilis was used as a strain to ferment yeast feed. The OD value and number of yeast cells were used as response values to optimize the medium components of the yeast feed through a response surface methodology. The optimal medium components were a glucose master liquor concentration of 8.3%, a corn steep liquor concentration of 1.2%, and a KH2PO4 concentration of 0.14%. Under this condition of fermentation, the OD value was 0.670 and the number of yeast cells was 2.72 × 108/mL. Then, we fed Candida utilis feed to Dongliao black piglets, and the effects of the yeast feed on the piglets' growth performance, fecal microbiota, and plasma metabolic levels were investigated through 16S rDNA sequencing and metabolomics. In total, 120 black piglets with an average initial weight of 6.90 ± 1.28 kg were randomly divided into two groups. One group was fed the basic diet (the CON group), and the other was supplemented with 2.5% Candida utilis add to the basic diet (the 2.5% CU group). After a pre-feeding period, the formal experiments were performed for 21 days. The results showed that the addition of Candida utilis to the diet did not affect growth performance compared with the control group. Meanwhile, no significant differences were observed in the serum biochemical indices. However, piglets in the 2.5% CU group had a significantly altered fecal microbiota, with an increased abundance of Clostridium_sensu_stricto_1, Lactobacillus, and Muribaculaceae_unclassified. Regarding the plasma metabolome, the 12 differential metabolites detected were mainly enriched in the histidine, tryptophan, primary bile acid, and caffeine metabolic pathways. Regarding the integrated microbiome-metabolome analysis, differential metabolites correlated with fecal flora to variable degrees, but most of them were beneficial bacteria of Firmicutes. Collectively, dietary Candida utilis feed had no adverse effect on growth performance; however, it played an important role in regulating fecal flora and maintaining metabolic levels.

Overproduction of bacterial cellulose from Acetobacter xylinum BPR2001 using food industries wastes.

In this study, a cost-effective complex culture media containing molasses and corn steep liquor (CSL) was developed for the high production of bacterial cellulose (BC) by investigating the effect of four effective factors on BC production at three levels using Taguchi and combined methods. The predicted and actual values of BC production in optimal conditions by Taguchi and combined methods were 8.41 and 14.52g/L, respectively. These results showed that the combined method was more suitable for predicting the optimal conditions in the optimization of BC production, the cost of developed culture medium was around 94% cost of HS medium preparation, molasses was the most effective factor in both experimental design methods, and initial pH adjustment had little impact on BC production. Then, the effect of inoculation conditions containing three factors of inoculation age, ethanol addition time, and agitation rate on the increase of BC production at three levels was investigated using the response surface methodology with the Box-Behnken design algorithm. Under the optimal conditions including inoculum age of 3 days, ethanol addition time of 10 days, and stirring speed of 100rpm, the predicted and experimental results of BC production were 21.61 and 20.21g/L, respectively. This is among the highest ever reported for BC production, which was achieved with a more cost-effective culture medium containing molasses and CSL.

Valorization of Corn Steep Liquor for Improved Value-added Products: A Review

Abstract: Corn steep liquor (CSL) is a by-product of wet steeping corn and is a source of vitamins, minerals, and amino acids. Depending on how food processing firms dispose of waste, CSL might have a negative impact on the environment. However, when CSL is used properly, it can promote economic growth and sustainability and prevent adverse environmental effects. However, the nutritional content of CSL and the high concentration of its organic matter suggest it is a rich source of feedstock. It can be used as a nutrient supplement or precursor to other products with even more value. CSL has been studied as a feedstock and additive for the sustainable production of chemicals and industrial products. A variety of bioproducts, including ethanol, acetoin, vanillin, and a variety of other biofuels, can be made from CSL due to its low cost and availability of components (nitrogen and carbon). The study seeks to highlight and present comprehensive novel uses of corn steep liquor in the circular economy to produce highervalued products with reduced carbon footprints.

Medium Optimization and Fermentation Kinetics for Antifungal Compounds Production by an Endophytic Paenibacillus polymyxa DS-R5 Isolated from Salvia miltiorrhiza.

An endophytic bacterium Paenibacillus polymyxa DS-R5 which can effectively inhibit the growth of pathogenic fungi was isolated from Salvia miltiorrhiza in our previous study. By using hydrochloric acid precipitation, methanol extraction, silica gel column isolation, dextran gel chromatography column, and HPLC, 3 compounds with antifungal activity were isolated. To further improve the production of antifungal compounds produced by this strain, fermentation medium was optimized using one-factor-at-a-time, Plackett-Burman design, and Box-Behnken design experiments. Through statistical optimization, the optimal medium composition was determined to be as follows: 14.7g/l sucrose, 20.0g/l soluble starch, 7.0g/l corn steep liquor, 10.0g/l(NH4)2SO4, and 0.7g/lKH2PO4. In this optimized medium, the highest titer of antifungal compounds reached 3452 U/ml, which was 123% higher than that in the initial medium. In addition, in order to guide scale-up for production, logistic and Luedeking-Piret equations were proposed to predict the cell growth and antifungal compounds production. The fermentation kinetics and empirical equations of the coefficients (X0, Xm, μm, α, and β) for the two models were reported, which will aid the design and optimization of industrial processes. The degrees of fit between calculated values of the model and the experimental data were 0.989 and 0.973, respectively. The results show that the cell growth and product synthesis models established in this study may better reflect the dynamic process of antifungal compounds production and provide a theoretical basis for further optimization and on-line monitoring of the fermentation process.

Efficient Production of Succinic Acid from Sugarcane Bagasse Hydrolysate by Actinobacillus succinogenes GXAS137

Sugarcane bagasse (SCB) is an abundant agricultural waste, rich in cellulose and hemicellulose, that could be used as an ideal raw material for succinic acid (SA) production. A two-step chemical pretreatment, involving alkali extraction and alkaline hydrogen peroxide treatment, was utilized to treat SCB, followed by multi-enzyme hydrolysis to obtain a reducing sugar hydrolysate mainly composed of glucose and xylose. Optimization of the multi-enzyme hydrolysis of pretreated SCB resulted in a final reducing sugar concentration of 78.34 g/L. In order to enhance the bioconversion of SCB to SA and to reduce the production costs, the initial reducing sugar concentration, nitrogen source, and MgCO3 content were further optimized. The results demonstrated that the inexpensive corn steep liquor powder (CSLP) could be utilized as an alternative nitrogen source to yeast extract for the production of SA; and the optimal concentrations of initial reducing sugar, CSLP, and MgCO3 were 70 g/L, 18 g/L, and 60 g/L, respectively. When fed-batch fermentation was conducted in a 2 L stirred bioreactor, approximately 72.9 g/L of SA was produced, with a yield of 83.2% and a productivity of 1.40 g/L/h. The high SA concentration, yield, and productivity achieved in this study demonstrate the potential of SCB, an agricultural waste, as a viable alternative substrate for Actinobacillus succinogenes GXAS137 to produce SA. This lays a solid foundation for the resource utilization of agricultural waste and cost-effective industrial-scale production of SA in the future.

Sustainable production of optically pure platform chemical bio-based (R,R)−2,3-butanediol from sugarcane molasses in a low-cost salt medium

Bio-based 2,3-butanediol (2,3-BDO) viability production on a large scale depends on the culture medium costs, fermentation broth, and bioprocess biosafety. This study investigated sugarcane molasses, corn steep liquor, and ammonium chloride to replace commercial glucose and yeast extract for 2,3-BDO production by a safe and wild-type Paenibacillus peoriae NRRL BD-62. A savings of 75.2% were achieved using sugarcane molasses and NH4Cl-based medium, whose final cost was 4.74 US$/kg2,3-BDO. Levo-2,3-BDO was produced with high optical purity and no acetoin accumulation in batch fermentation. The selectivity was maintained above 90% in fed-batch fermentation at constant feeding. In contrast, the yield showed a 20% reduction, indicating that this feeding strategy was less efficient than batch cultures. To the best of our knowledge, this is the first time that levo-2,3-BDO with high optical purity has been produced by a newly isolated P. peoriae strain from sugarcane molasses in a low-cost salt medium, making the large-scale process sustainably promising.

Exploring the use of hexadecane by Yarrowia lipolytica: Effect of dissolved oxygen and medium supplementation

This work aimed to evaluate the effect of medium composition and volumetric oxygen transfer coefficient (kLa) on Y. lipolytica growth and production of microbial lipids and enzymes from hexadecane. In the stirred tank bioreactor, increasing kLa from 11 h−1 to 132 h−1 improved the hexadecane assimilation rate, biomass concentration, and lipids synthesis (0.90 g·L−1). A cost-effective hexadecane-based medium supplemented with corn steep liquor and a low amount of ammonium sulfate boosted lipids production up to 2.1 g·L−1, composed of palmitic, palmitoleic, oleic, and linoleic acids. The unsaturated/saturated fraction was dependent on the C/N ratio. Lipids of Y. lipolytica CBS 2075 are promising feedstock for animal feed, food additives, or the biodiesel industry. Simultaneous synthesis of extracellular lipase and protease from hexadecane was observed, which is a new feature that was not previously reported. The highest enzyme activity was obtained at the highest C/N ratio conditions. These results open new perspectives on the application of Y. lipolytica-based cultures for the biotransformation of hexadecane-polluted streams into valuable compounds, fulfilling an interesting strategy towards the circular economy concept.

Synergistic approach for enhanced production of polyhydroxybutyrate by Bacillus pseudomycoides SAS-B1: Effective utilization of glycerol and acrylic acid through fed-batch fermentation and its environmental impact assessment

The continual rise in the consumption of petroleum-based synthetic polymers raised a significant environmental concern. Bacillus pseudomycoides SAS-B1 is a gram-positive rod-shaped halophilic bacterium capable of accumulating Polyhydroxybutyrate (PHB)-an intracellular biodegradable polymer. In the present study, the optimal conditions for cell cultivation in the seed media were developed. The optimal factors included a preservation age of 14 to 21 days (with 105 to 106 cells/mL), inoculum size of 0.1 % (w/v), 1 % (w/v) glucose, and growth temperature of 30 °C. The cells were then cultivated in a two-stage fermentation process utilizing glycerol and Corn Steep Liquor (CSL) as carbon and nitrogen sources, respectively. PHB yield was effectively increased from 2.01 to 9.21 g/L through intermittent feeding of glycerol and CSL, along with acrylic acid. FTIR, TGA, DSC, and XRD characterization studies were employed to enumerate the recovered PHB and determine its physicochemical properties. Additionally, the study assessed the cradle-to-gate Life Cycle Assessment (LCA) of PHB production, considering net CO2 generation and covering all major environmental impact categories. The production of 1000 kg of PHB resulted in lower stratospheric ozone depletion and comparatively reduced carbon dioxide emissions (2022.7 kg CO2 eq.) and terrestrial ecotoxicity (9.54 kg 1,4-DCB eq.) than typical petrochemical polymers.