Biorefinery for Glycerol Rich Biodiesel Industry Waste

Turning waste into treasure: A new direction for low-cost production of lipid chemicals from Thraustochytrids

Thraustochytrids are marine microorganisms known for their fast growth and ability to store lipids, making them useful for producing polyunsaturated fatty acids (PUFAs), biodiesel, squalene, and carotenoids. However, the high cost of production, mainly due to expensive fermentation components, limits their wider use. A significant challenge in this context is the need to balance production costs with the value of the end products. This review focuses on integrating the efficient utilization of waste with Thraustochytrids fermentation, including the economic substitution of carbon sources, nitrogen sources, and fermentation water. This approach aligns with the 3Rs principles (reduction, recycling, and reuse). Furthermore, it emphasizes the role of Thraustochytrids in converting waste into lipid chemicals and promoting sustainable circular production models. The aim of this review is to emphasize the value of Thraustochytrids in converting waste into treasure, providing precise cost reduction strategies for future commercial production.

Exploiting Polyhydroxyalkanoates for Biomedical Applications

Polyhydroxyalkanoates (PHA) are biodegradable plastic. Numerous bacteria produce PHAs under environmental stress conditions, such as excess carbon-rich organic matter and limitations of other nutritional elements such as potassium, magnesium, oxygen, phosphorus, and nitrogen. In addition to having physicochemical properties similar to fossil-fuel-based plastics, PHAs have unique features that make them ideal for medical devices, such as easy sterilization without damaging the material itself and easy dissolution following use. PHAs can replace traditional plastic materials used in the biomedical sector. PHAs can be used in a variety of biomedical applications, including medical devices, implants, drug delivery devices, wound dressings, artificial ligaments and tendons, and bone grafts. Unlike plastics, PHAs are not manufactured from petroleum products or fossil fuels and are, therefore, environment-friendly. In this review, a recent overview of applications of PHAs with special emphasis on biomedical sectors, including drug delivery, wound healing, tissue engineering, and biocontrols, are discussed.

Improved fed-batch processes with Wickerhamomyces anomalus WC 1501 for the production of D-arabitol from pure glycerol

BACKGROUND

D-Arabitol, a five-carbon sugar alcohol, represents a main target of microbial biorefineries aiming to valorize cheap substrates. The yeast Wickerhamomyces anomalus WC 1501 is known to produce arabitol in a glycerol-based nitrogen-limited medium and preliminary fed-batch processes with this yeast were reported to yield 18.0 g/L arabitol.

RESULTS

Fed-batch fermentations with W. anomalus WC 1501 were optimized using central composite design (CCD). Dissolved oxygen had not a significant effect, while optimum values were found for glycerol concentration (114.5 g/L), pH (5.9), and temperature (32.5 °C), yielding 29 g/L D-arabitol in 160 h, a conversion yield of 0.25 g of arabitol per g of consumed glycerol, and a volumetric productivity of 0.18 g/L/h. CCD optimal conditions were the basis for further improvement, consisting in increasing the cellular density (3✕), applying a constant feeding of glycerol, and increasing temperature during production. The best performing fed-batch fermentations achieved 265 g/L D-arabitol after 325 h, a conversion yield of 0.74 g/g, and a volumetric productivity of 0.82 g/L/h.

CONCLUSION

W. anomalus WC 1501 confirmed as an excellent producer of D-arabitol, exhibiting a remarkable capability of transforming pure glycerol. The study reports among the highest values ever reported for microbial transformation of glycerol into D-arabitol, in terms of arabitol titer, conversion yield, and productivity.

Algae application in civil construction: A review with focus on the potential uses of the pelagic Sargassum spp. biomass

Pelagic Sargassum, usually found at the Sargasso Sea and the Western portion of the North Atlantic and Gulf of Mexico, has been detected in many new locations through the tropical Atlantic. The huge biomass found from the African coast to the Caribbean was called the Great Atlantic Sargassum Belt and is responsible for the stranding of tons of algae on coastal regions. Despite the environmental, social, and economic impacts, sargassum is a valuable source for multiple uses at the industry, such as alginates, cosmetics, recycled paper and bioplastics, fertilizers, and as raw material for civil construction. This work presents a systematic literature review on the use of algae at the civil construction sector, with a focus on the valorization of the pelagic Sargassum spp. biomass, by identifying the potential applications related to the use of other algal species. The review considered other genera of marine algae and marine angiosperms, resulting in a total of 31 selected articles. The marine grass Posidonia oceanica was the most used species, found in eight published papers, followed by the red alga Kappaphycus alvarezii with four studies. Two articles were available on the use of pelagic Sargassum spp. (S. fluitans and S.natans) for construction materials (adobe and pavement), with potential good results. The literature presented results from the use of marine algae and sea grasses for particleboards, polymeric and cemented composites, adobe, pavement, facades, and roofs. This article provides a state-of-the-art review of algal application in the civil construction sector and points out the main directions for the potentialities on the insertion of the Sargassum spp. biomass into the production chain of the sector.

Exploring the environmental traits and applications of Klebsiella variicola

Klebsiella variicola has been found in various natural niches, alone or in association with other bacteria, and causes diseases in animals and plants with important economic and environmental impacts. K. variicola has the capacity to fix nitrogen in the rhizosphere and soil; produces indole acetic acid, acetoin, and ammonia; and dissolves phosphorus and potassium, which play an important role in plant growth promotion and nutrition. Some members of K. variicola have properties such as halotolerance and alkalotolerance, conferring an evolutionary advantage. In the environmental protection, K. variicola can be used in the wastewater treatment, biodegradation, and bioremediation of polluted soil, either alone or in association with other organisms. In addition, it has the potential to carry out industrial processes in the food and pharmaceutical industries, like the production of maltose and glucose by the catalysis of debranching unmodified oligosaccharides by the pullulanase enzyme. Finally, this bacterium has the ability to transform chemical energy into electrical energy, such as a biocatalyst, which could be useful in the near future. These properties show that K. variicola should be considered an eco-friendly bacterium with hopeful technological promise. In this review, we explore the most significant aspects of K. variicola and highlight its potential applications in environmental and biotechnological processes.

Overexpression of Citrate Synthase Increases Isocitric Acid Biosynthesis in the Yeast Yarrowia lipolytica

Yarrowia lipolytica is a non-conventional yeast producing valuable compounds, such as citric acids, from renewable raw materials. This study investigated the impact of citrate synthase overexpression on the biosynthesis of citric and isocitric acid in Y. lipolytica. Two transformants of Y. lipolytica A101.1.31 strain (efficient citric acid producer), overexpressing CIT1 or CIT2 gene (encoding proteins with citrate synthase activity), were constructed. The results revealed that overexpression of either of these genes enhances citrate synthase activity. Additionally, the cit1 knockout strain was unable to use propionate as the sole carbon source, which proves that CIT1 gene encodes a dual activity protein–citrate and 2-methylcitrate synthase. In the overexpressing mutants, a significant increase in isocitric acid biosynthesis was observed. Both CIT1 and CIT2 overexpressing strains produced citric and isocitric acid from vegetable oil in a ratio close to 1 (CA/ICA ratio for wild-type strain was 4.12).

Biochemical conversion of biodiesel by-product into malic acid: A way towards sustainability

Crude glycerol, one of the ever-growing by-product of biodiesel industry and is receiving the closest review in recent times because direct disposal of crude glycerol may emerge ecological issues. The renewability, bioavailability and typical structure of glycerol, therefore, discover conceivable application in serving the role of carbon and energy source for microbial biosynthesis of high value products. This conceivable arrangement could find exploitation of crude glycerol as a renewable building block for bio-refineries as it is economically as well as environmentally profitable. In this review, we summarize the uptake and catabolism of crude glycerol by different wild and recombinant microorganism. The chemical and biochemical transformation of crude glycerol into high esteem malic acid by various microbial pathways is also additionally discussed. An extensive investigation in the synthesis of high-value malic acid production from various feed stock which finds applications in cosmeceutical and chemical industries, food and beverages, and to some extent in the field of medical science is also likewise studied. Finally, the open doors for unrefined crude glycerol in serving as a promising abundant energy source for malic acid production in near future have been highlighted.

Impact of the Type of Fertilization and the Addition of Glycerol on the Quality of Spring Rape Straw Pellets

This paper presents an analysis of selected qualitative characteristics of pellets produced from rape straw obtained from cultivations subjected to different fertilization treatments and from mixtures of straw selected for testing with crude glycerol obtained as a by-product from biodiesel production. The assessment focused on the following qualities of the obtained pellets: Moisture content, mechanical durability, heating value and main elements, that is, carbon, hydrogen, nitrogen, sulphur, chlorine and oxygen. The obtained results indicated that the different treatment regimens applied in spring rape cultivations had a significant impact on the physicochemical qualities of the straw. In terms of the heating value, traditional fertilization with multi-component fertilizer (NPK) yielded slightly lower chemical parameters (lower carbon content and heat of combustion) than in the case of straw obtained from the control sample and from the plot fertilized with digestate. Furthermore, in all of the analysed mixtures, the 10% addition of raw glycerol improved the mechanical characteristics of the produced straw pellets. After the 10% glycerol addition, in terms of the energetic use of these biofuels, the parameters of the fuel, such as heating value and net heating value, were slightly decreased.

Aligning Microbial Biodiversity for Valorization of Biowastes: Conception to Perception

Generation of biowastes is increasing rapidly and its uncontrolled, slow and persistent fermentation leads to the release of Green-house gases (GHGs) into the environment. Exploration and exploitation of microbial diversity for degrading biowastes can result in producing diverse range of bioactive molecules, which can act as a source of bioenergy, biopolymers, nutraceuticals and antimicrobials. The whole process is envisaged to manage biowastes, and reduce their pollution causing capacity, and lead to a sustainable society. A strategy has been proposed for: (1) producing bioactive molecules, and (2) achieving a zero-pollution emission by recycling of the GHGs through biological routes.

Optimisation of a modified submerged bed biofilm reactor for biological oleochemical wastewater treatment

Oleochemicals industry effluence mainly contains a high chemical oxygen demand (COD) in a range of 6000-20,000 ppm. An effective biological wastewater treatment process must be carried out before wastewater is discharged into the environment. In this study, a submerged bed biofilm reactor (SBBR) was adapted to the biological oleochemical wastewater treatment plant observed in the present study. The effect of wastewater flow rate (100-300 mL/min), Cosmoball^® percentage in the SBBR system (25-75%), and percentage of activated sludge (0-50%) were investigated in terms of COD reduction. The Box-Behnken design was used for response surface methodology (RSM) and to create a set of 18 experimental runs, which was needed for optimising the biological oleochemical wastewater treatment. A quadratic polynomial model with estimated coefficients was developed to describe COD reduction patterns. The analysis of variance (ANOVA) shows that the wastewater flow rate was the most effective factor in reducing COD, followed by activated sludge percentage and Cosmoball^® carrier percentage. Under the optimum conditions (i.e., a wastewater flow rate of 103.25 mL/min a Cosmoball^® carrier percentage of 71.94%, and an activated sludge percentage of 40.50%) a COD reduction of 98% was achieved. Thus, under optimum conditions, as suggested by the BBD, SBBR systems can be used as a viable means of biological wastewater treatment in the oleochemicals industry.

Bio-hydrogen production by co-digestion of domestic wastewater and biodiesel industry effluent

The increasing water crisis makes fresh water a valuable resource, which must be used wisely. However, with growing population and inefficient waste treatment systems, the amount of wastewater dispelled in rivers is increasing abominably. Utilizing this freely available waste-water along with biodiesel industry waste- crude glycerol for bio-hydrogen production is being reported here. The bacterial cultures of Bacillus thuringiensis strain EGU45 and Bacillus amyloliquefaciens strain CD16 produced2.4-3.0 L H2/day/L feed during a 60 days continuous culture system at hydraulic retention time of 2 days. An average H2 yield of 100-120 L/L CG was reported by the two strains. Recycling of the effluent by up to 25% resulted in up to 94% H2 production compared to control.

Production of gellan gum, an exopolysaccharide, from biodiesel-derived waste glycerol by Sphingomonas spp

In the present study, biodiesel-derived waste glycerol (WG) was used for the isolation and production of gellan, an exopolysaccharide, on media containing WG as the main carbon source. Two bacterial isolates showed gellan producing potential which were identified as Sphingomonas pseudosanguinis (Accession No. GI:724472387) and Sphingomonas yabuuchiae (GI:724472388) by 16S rRNA gene sequencing. To maximize gellan production by S. pseudosanguinis and S. yabuuchiae, media optimization was performed at different pHs and glycerol concentrations. Morphological observations through microscopic images showed the production of gellan from these isolates. Simple linear regression showed better utilization of WG by S. pseudosanguinis than S. yabuuchiae at pH 6 and pH 7. Though, both the strains showed reverse trend at pH 8. Both the strains were able to produce high amounts of gellan gum (51.6 and 52.6 g/l, respectively) using WG (80 g/l) as the sole carbon source, in a minimal medium. This is the first report on the efficient degradation of WG and low-cost production of gellan. Owing to these characteristics, S. pseudosanguinis and S. yabuuchiae demonstrate great potential for use in the commercial production of gellan and in the bioremediation of WG.

Wastewater: A Potential Bioenergy Resource

Wastewaters are a rich source of nutrients for microorganisms. However, if left unattended the biodegradation may lead to severe environmental hazards. The wastewaters can thus be utilized for the production of various value added products including bioenergy (H₂ and CH₄). A number of studies have reported utilization of various wastewaters for energy production. Depending on the nature of the wastewater, different reactor configurations, wastewater and inoculum pretreatments, co-substrate utilizations along with other process parameters have been studied for efficient product formation. Only a few studies have reported sequential utilization of wastewaters for H₂ and CH₄ production despite its huge potential for complete waste degradation.

Co-utilization of Crude Glycerol and Biowastes for Producing Polyhydroxyalkanoates

Polyhydroxyalkanoate (PHA) production by Bacillus thuringiensis EGU45 and defined mixed culture of Bacillus spp. were studied by using crude glycerol (CG) and hydrolyzed biowastes as feed material. Hydrolysates from onion peels (OP), potato peels, pea-shells (PS), apple pomace 2% total solids obtained with defined mixed hydrolytic cultures (MHC2) were inoculated with B. thuringiensis EGU45 and defined mixed bacterial cultures (5MC1), which produced PHA at the rate of 40-350 and 65-450 mg/L, respectively. Addition of CG (1%, v/v) to these hydrolysates resulted in 1.8-fold and 4.5-fold enhancement in PHA production from OP by B. thuringiensis EGU45 and 5MC1, respectively. Co-utilization of OP and PS (in 2:1 ratio) supplemented with CG (1%, v/v) by B. thuringiensis EGU45 resulted in 2-fold increase in PHA production in comparison to OP + CG. This co-metabolism of OP and PS also enabled PHA co-polymer production (1300 mg/L), having an enhanced HV content of 21.2% (w/w).

Bioprocessing of Biodiesel Industry Effluent by Immobilized Bacteria to Produce Value-Added Products

Biodiesel industrial effluent rich in crude glycerol (CG) was processed to produce value-added product. Under continuous culture system, Bacillus amyloliquefaciens strain CD16 immobilized within its biofilm, produced 3.2 L H₂/day/L feed, over a period of 60 days at a hydraulic retention time of 2 days. The effective H₂ yield by B. amyloliquefaciens strain CD16 was 165 L/L CG. This H₂ yield was 1.18-fold higher than that observed with non-biofilm forming Bacillus thuringiensis strain EGU45. Bioprocessing of the effluent released after this stage, by recycling it up to 25% did not have any adverse effect on H₂ production by strain EGU45; however, a 25% reduction in yield was recorded with strain CD16. Biofilm forming H₂ producers thus proved effective as self-immobilizing system leading to enhanced process efficiency.

Polyhydroxyalkanoate Production and Degradation Patterns in Bacillus Species

Bacteria under stress conditions of excess of carbon (C) and limitations of nutrients divert its metabolism towards C storage as energy reservoir-polyhydroxyalkanoate (PHA). Different Bacillus species-B. cereus and B. thuringiensis, were monitored to produce PHA from different C sources-glucose, crude glycerol and their combination at 37 °C for period up to 192 h. PHA production and its composition was found to vary with feed and bacterial strains. PHA production on crude glycerol continued to increase up to 120 h, reaching a maximum of 2725 mg/L with an effective yield of 71% of the dry cell mass. Depolymerization of PHA was observe to initiate after 96 h of incubation up to 192 h. PHA degradation products have been envisaged to be applied in medical field: tissue engineering, drug carriers, memory enhancers, antiosteoporosis, biodegradable implants. The PHA production and degradation cycle for 192 h has not been reported previously in literature.

Nanoparticles in Biological Hydrogen Production: An Overview

Biological hydrogen (H₂) production enhancement through the use of nanoparticles (NPs) supplement in the media is being recognized as a promising approach. The NPs, including those of metal and metal oxides have shown a significant improvement in the BHP. A number of organisms as pure or mixed cultures can produce H₂ in presence of NPs from pure sugars and biowaste as a feed. However, their H₂ production efficiencies have been found to vary significantly with the type of NPs and their concentration. In this review article, the potential role of NPs in the enhancement of H₂ production has been assessed in dark- and photo-fermentative organisms using sugars and biowaste materials as feed. Further, the integrative approaches for commercial applications of NPs in BHP have been discussed.

Biomedical Applications of Polyhydroxyalkanoates

Polyhydroxyalkanoates (PHA) are produced by a large number of microbes under stress conditions such as high carbon (C) availability and limitations of nutrients such as nitrogen, potassium, phosphorus, magnesium, and oxygen. Here, microbes store C as granules of PHAs-energy reservoir. PHAs have properties, which are quite similar to those of synthetic plastics. The unique properties, which make them desirable materials for biomedical applications is their biodegradability, biocompatibility, and non-toxicity. PHAs have been found suitable for various medical applications: biocontrol agents, drug carriers, biodegradable implants, tissue engineering, memory enhancers, and anticancer agents.

Dark-Fermentative Biological Hydrogen Production from Mixed Biowastes Using Defined Mixed Cultures

Biological hydrogen (H₂) production from the biowastes is widely recognized as a suitable alternative approach to utilize low cost feed instead of costly individual sugars. In the present investigation, pure and mixed biowastes were fermented by defined sets of mixed cultures for hydrolysis and H₂ production. Under batch conditions, up to 65, 67 and 70 L H₂/kg total solids (2%, TS) were evolved from apple pomace (AP), onion peels (OP) and potato peels (PP) using a combination of hydrolytic mixed culture (MHC5) and mixed microbial cultures (MMC4 or MMC6), respectively. Among the different combinations of mixed biowastes including AP, OP, PP and pea-shells, the combination of OP and PP exhibited maximum H₂ production of 73 and 84 L/kg TS with MMC4 and MMC6, respectively. This study suggested that H₂ production can be effectively regulated by using defined sets of mixed cultures for hydrolysis and H₂ production from pure and mixed biowastes as feed even under unsterile conditions.

Co-metabolism of substrates by Bacillus thuringiensis regulates polyhydroxyalkanoate co-polymer composition

Polyhydroxyalkanoate (PHA) production by Bacillus thuringiensis EGU45 was studied by co-metabolism of crude glycerol (CG) (1%, v/v), glucose (0.05-0.5%, w/v) and propionic acid (0.05-0.5%, v/v) under batch (shake flask) culture conditions. Glycerol+PA combination resulted in 15-100mg/L PHA co-polymers with a HV content of 33-81mol%. The addition of NH₄Cl (0.5%, w/v) to CG+PA enhanced PHA production by 1.55-fold, with a HV content of 58-70mol%. The time period of incubation of PA to the feed: CG+glucose was optimized to be 3h after initiation of fermentation. The PHA contents were found to be stable at 1900-2050mg/L up scaling from 0.4 to 2.0L feed material. Biochemical characterization through GC-MS of PHA co-polymer revealed the presence of 3-hydroxydecanoate (3-HDD), 3-hydroxyoctadecanoate (3HOD), 3-hydroxyhexadecanoate (3HHD).

Integrative Approach for Producing Hydrogen and Polyhydroxyalkanoate from Mixed Wastes of Biological Origin

In this study, an integrative approach to produce biohydrogen (H2) and polyhydroxyalkanoates (PHA) from the wastes of biological origin was investigated. A defined set of mixed cultures was used for hydrolysis and the hydrolysates were used to produce H2. The effluent from H2 production stage was used for PHA production. Under batch culture, a maximum of 62 l H2/kg of pure potato peels (Total solid, TS 2 %, w/v) and 54 l H2/kg of mixed biowastes (MBW1) was recorded. Using effluent from the H2 production stage of biowaste mixture (MBW1), Bacillus cereus EGU43 could produce 195 mg PHA/l and 15.6 % (w/w). Further, supplementation of GM-2 medium (0.1×) and glucose (0.5 %) in H2 production stage effluents, resulted in significant improvements of up to 11 and 41.7 % of PHA contents, respectively. An improvement of 3.9- and 17-fold in PHA yields as compared to with and without integrative H2 production from the MBW1 has been recorded. This integrative approach seems to be a suitable process to improve the yields of H2 and PHA by mixing biowastes.