Techno-economic risk assessment, life cycle analysis and life cycle costing for poly(butylene succinate) and poly(lactic acid) production using renewable resources.

The sustainable production of poly(lactic acid) (PLA) or poly(butylene succinate) (PBS) from corn glucose syrup, corn stover and sugar beet pulp (SBP) have been assessed via process design, preliminary techno-economic evaluation, life cycle assessment and life cycle costing (LCC). Cost-competitive PLA and PBS production can be achieved in a SBP-based biorefinery, including separation of crude pectin-rich extract as co-product, leading to minimum selling prices of $1.14/kgPLA and $1.37/kgPBS. Acidification Potential, Eutrophication Potential and Human Toxicity Potential are lower when SBP is used. The LCC of PLA ($1.42/kgPLA) and PBS ($1.72/kgPBS) production from SBP are lower than biaxial oriented polypropylene (BOPP, $1.66/kg) and general purpose polystyrene (GPPS, $2.04/kg) at pectin-rich extract market prices of $3/kg and $4/kg, respectively. Techno-economic risk assessment via Monte-Carlo simulations showed that PLA and PBS could be produced from SBP at the market prices of BOPP ($1.4/kg) and GPPS ($1.72/kg) with 100% probability to achieve a positive Net Present Value at pectin-rich extract market prices of $3/kg and $4/kg, respectively. This study demonstrated that SBP-based biorefinery development ensures sustainable production of PLA and PBS as compared to fossil-derived counterparts and single product bioprocesses using glucose syrup and corn stover.

Techno-economic evaluation and life cycle assessment of a biorefinery using winery waste streams for the production of succinic acid and value-added co-products.

This study presents techno-economic evaluation and life cycle assessment of a novel biorefinery using the three main waste streams generated by wineries for the production of bio-based succinic acid (SA), crude phenolic-rich extract, grape-seed oil, calcium tartrate and crude tannin-rich extract. Process design has been employed for the estimation of material and energy balances and the sizing of unit operations. The Minimum Selling Price of succinic acid production within a winery waste biorefinery ranges from $1.23-2.76/kgSA depending on the market price and the potential end-uses of the extracted fractions. The Global Warming Potential and the Abiotic Depletion Potential of winery waste valorisation through the proposed biorefinery are 1.47 kg CO2-eq per kg dry waste and 25.2 MJ per kg dry waste, respectively. Biorefining of winery waste could lead to the development of a sustainable and novel bioeconomy business model with new market opportunities and efficient waste management.

Techno-economic evaluation and life-cycle assessment of poly(3-hydroxybutyrate) production within a biorefinery concept using sunflower-based biodiesel industry by-products.

This study presents techno-economic evaluation of a biorefinery concept using biodiesel industry by-products (sunflower meal and crude glycerol) to produce poly(3-hydroxybutyrate) (PHB), crude phenolic extracts (CPE) and protein isolate (PI). The PHB production cost at two annual production capacities ($12.5/kg for 2,500 t PHB/year and $7.8/kg for 25,000 t PHB/year) was not cost-competitive to current PHB production processes when the revenues derived from co-products were not considered. Sensitivity analysis projected the economic viability of a biorefinery concept that could achieve a minimum selling price of $1.1/kg PHB similar to polypropylene. The annual PHB production capacity and the identification of marketable end-uses with respective market prices for the co-products CPE and PI were crucial in attaining process profitability. Greenhouse gas emissions (ca. 0.64 kg CO2-eq/kg PHB) and abiotic depletion potential (61.7 MJ/kg PHB) were lower than polypropylene. Biorefining of sunflower meal and crude glycerol could lead to sustainable PHB production.

Sustainable production of bio-based chemicals and polymers via integrated biomass refining and bioprocessing in a circular bioeconomy context.

The sustainable production of bio-based chemicals and polymers is highly dependent on the development of viable biorefinery concepts using crude renewable resources for the production of diversified products. Within this concept, this critical review presents the availability of fractionated co-products and fermentable sugars that could be derived from major industrial and food supply chain side streams in EU countries. Fermentable sugars could be used for the production of bio-based chemicals and polymers. The implementation of biorefinery concepts in industry should depend on the evaluation of process efficiency and sustainability including techno-economic, environmental and social impact assessment following circular bioeconomy principles. Relevant sustainability indicators and End-of-Life scenarios have been presented. A case study on the techno-economic evaluation of bio-based succinic acid production from the organic fraction of municipal solid waste has been presented focusing on the evaluation of process profitability and feedstock requirements.

A newly isolated Enterobacter sp. strain produces 2,3-butanediol during its cultivation on low-cost carbohydrate-based substrates.

2,3-Butanediol (BDO) is an important platform chemical with a wide range of applications in various industries. In the present study, a newly isolated wild Enterobacter sp. strain (FMCC-208) was evaluated towards its ability to produce BDO on media composed of sugars derived from sucrose refinery plant. Optimum values of temperature and pH as well as substrate inhibition were determined through batch experiments. The ability of the strain to convert various monosaccharides was also investigated. Maximum BDO concentrations of 90.3 and 10 g l-1 of acetoin were obtained during a fed-batch bioreactor experiment with cane molasses and sucrose employed as substrates. A high volumetric productivity was noted in a fed-batch experiment using molasses and sucrose as carbon sources at T = 37°C, in which 73.0 g l-1 of BDO together with 12.4 g l-1 of acetoin was produced where 1.15 g l-1 h-1 of diol/acetoin was produced. In previously pasteurized media, 70.0 g l-1 of BDO and 5.0 g l-1 of acetoin were produced (yield = 0.39 g g-1). Finally, besides BDO production, growth on molasses was accompanied by non-negligible decolorization (25-35%) of the residue. Therefore, the strain is a promising candidate for the conversion of sucrose-based materials into BDO.

Improvement on bioprocess economics for 2,3-butanediol production from very high polarity cane sugar via optimisation of bioreactor operation.

This study focuses on the optimisation of 2,3-butanediol (BDO) production in fed-batch cultures carried out with the bacterial strain Enterobacter ludwigii using very high polarity (VHP) sugar from sugarcane mills. Various kLa values were evaluated using either complex or synthetic fermentation media demonstrating that the latter enhance BDO production efficiency with low by-product formation. The pH (6.3) and temperature (33.9 °C) employed in fed-batch bioreactor cultures has been optimised via experimental design. Fed-batch cultures carried out at the optimum temperature and pH and varying kLa values resulted in BDO concentration, yield and productivity of 86.8 g/L, 0.37 g/g and 3.95 g L-1 h-1. Using this fermentation efficiency, the minimum selling price of BDO for annual production capacities of 10,000 t and 50,000 t was estimated at $3.12/kg and $2.67/kg, respectively, for a VHP cane sugar market price of $0.4/kg.

Conversion of biodiesel-derived glycerol into biotechnological products of industrial significance by yeast and fungal strains.

Oleochemical activities (e.g. biodiesel production, fat saponification) generate annually very high amounts of concentrated glycerol-containing waters (called crude glycerol) as the principal residues of these processes. Crude glycerol is an industrial residue the valorization of which attracts remarkable and constantly increasing interest. In the current investigation, biodiesel-derived glycerol was employed as substrate for yeast and fungal strains cultivated under nitrogen-limited conditions in shake flasks. Glucose was employed as reference substrate. Several yeasts (Candida diddensiae, Candida tropicalis, Pichia ciferrii, Williopsis saturnus, Candida boidinii, and Candida oleophila) rapidly assimilated glucose and converted it into ethanol, despite aerobic conditions imposed, and were Crabtree-positive. None of these yeasts produced ethanol during growth on glycerol or accumulated significant quantities of lipid during growth on glucose or glycerol. Only Rhodosporidium toruloides produced notable lipid quantities from glucose and to lesser extent from glycerol. Yarrowia lipolytica LFMB 20 produced citrate ≈58 g/L growing on high-glucose media, while on high-glycerol media ≈42 g/L citrate and ≈18 g/L mannitol. During growth on glucose/glycerol blends, glycerol was assimilated first and thereafter glucose was consumed. Fungi produced higher lipid quantities compared with yeasts. High lipid quantities were produced by Mortierella ramanniana, Mucor sp., and mainly Mortierella isabellina, with glycerol being more adequate for M. ramanniana and glucose for Mucor sp. and M. isabellina. M. isabellina ATHUM 2935 produced lipids of 8.5 g/L, 83.3% w/w in dry cell weight (DCW) and conversion yield per unit of glucose consumed ≈0.25 g/g. The respective values on glycerol were 5.4 g/L, 66.6% w/w in DCW and ≈0.22 g/g. Lipids of all microorganisms were analyzed with regards to their fatty acid composition, and M. isabellina presented the closest similitude with rapeseed oil. Crude lipids produced by this fungus and extracted with chloroform/methanol blend, were composed mostly of triacylglycerols, thus indicating that these solvents are adequate for triacylglycerol extraction.

Production of added-value metabolites by Yarrowia lipolytica growing in olive mill wastewater-based media under aseptic and non-aseptic conditions.

Yarrowia lipolytica ACA-YC 5033 was grown on glucose-based media in which high amounts of olive mill wastewaters (OMWs) had been added. Besides shake-flask aseptic cultures, trials were also performed in previously pasteurized media while batch bioreactor experiments were also done. Significant decolorization (∼58%) and remarkable removal of phenolic compounds (∼51% w/w) occurred, with the latter being amongst the highest ones reported in the international literature, as far as yeasts were concerned during their growth on phenol-containing media. In nitrogen-limited flask fermentations the microorganism produced maximum citric acid quantity ≈19.0 g/L [simultaneous yield of citric acid produced per unit of glucose consumed (YCit/Glc)≈0.74 g/g]. Dry cell weight (DCW) values decreased at high phenol-containing media, but, on the other hand, the addition of OMWs induced reserve lipid accumulation. Maximum citric acid concentration achieved (≈52.0 g/L; YCit/Glc≈0.64 g/g) occurred in OMW-based high sugar content media (initial glucose added at ≈80.0 g/L). The bioprocess was successfully simulated by a modified logistic growth equation. A satisfactory fitting on the experimental data occurred while the optimized parameter values were found to be similar to those experimentally measured. Finally, a non-aseptic (previously pasteurized) trial was performed and its comparison with the equivalent aseptic experiment revealed no significant differences. Yarrowia lipolytica hence can be considered as a satisfactory candidate for simultaneous OMWs bioremediation and the production of added-value compounds useful for the food industry.

Optimal design of upstream processes in biotransformation technologies.

In this work a mathematical programming model for the optimal design of the bioreaction section of biotechnological processes is presented. Equations for the estimation of the equipment cost derived from a recent publication by the US National Renewable Energy Laboratory (NREL) are also summarized. The cost-optimal design of process units and the optimal scheduling of their operation can be obtained using the proposed formulation that has been implemented in software available from the journal web page or the corresponding author. The proposed optimization model can be used to quantify the effects of decisions taken at a lab scale on the industrial scale process economics. It is of paramount important to note that this can be achieved at the early stage of the development of a biotechnological project. Two case studies are presented that demonstrate the usefulness and potential of the proposed methodology.

Magnetically modified bacterial cellulose: A promising carrier for immobilization of affinity ligands, enzymes, and cells.

Bacterial cellulose (BC) produced by Komagataeibacter sucrofermentans was magnetically modified using perchloric acid stabilized magnetic fluid. Magnetic bacterial cellulose (MBC) was used as a carrier for the immobilization of affinity ligands, enzymes and cells. MBC with immobilized reactive copper phthalocyanine dye was an efficient adsorbent for crystal violet removal; the maximum adsorption capacity was 388mg/g. Kinetic and thermodynamic parameters were also determined. Model biocatalysts, namely bovine pancreas trypsin and Saccharomyces cerevisiae cells were immobilized on MBC using several strategies including adsorption with subsequent cross-linking with glutaraldehyde and covalent binding on previously activated MBC using sodium periodate or 1,4-butanediol diglycidyl ether. Immobilized yeast cells retained approximately 90% of their initial activity after 6 repeated cycles of sucrose solution hydrolysis. Trypsin covalently bound after MBC periodate activation was very stable during operational stability testing; it could be repeatedly used for ten cycles of low molecular weight substrate hydrolysis without loss of its initial activity.

Valorisation of side streams from wheat milling and confectionery industries for consolidated production and extraction of microbial lipids.

Crude enzymes produced via solid state fermentation (SSF) using wheat milling by-products have been employed for both fermentation media production using flour-rich waste (FRW) streams and lysis of Rhodosporidium toruloides yeast cells. Filter sterilization of crude hydrolysates was more beneficial than heat sterilization regarding yeast growth and microbial oil production. The initial carbon to free amino nitrogen ratio of crude hydrolysates was optimised (80.2g/g) in fed-batch cultures of R. toruloides leading to a total dry weight of 61.2g/L with microbial oil content of 61.8% (w/w). Employing a feeding strategy where the glucose concentration was maintained in the range of 12.2-17.6g/L led to the highest productivity (0.32 g/L·h). The crude enzymes produced by SSF were utilised for yeast cell treatment leading to simultaneous release of around 80% of total lipids in the broth and production of a hydrolysate suitable as yeast extract replacement.

Techno-economic evaluation of a complete bioprocess for 2,3-butanediol production from renewable resources.

This study presents the techno-economic evaluation of 2,3-butanediol (BDO) production via fermentation using glycerol, sucrose and sugarcane molasses as carbon sources. Literature-cited experimental data were used to design the fermentation stage, whereas downstream separation of BDO was based on reactive extraction of BDO employing an aldehyde to convert BDO into an acetal that is immiscible with water. The selected downstream process can be used in all fermentations employed. Sensitivity analysis was carried out targeting the estimation of the minimum selling price (MSP) of BDO at different plant capacities and raw material purchase costs. In all cases, the MSP of BDO is higher than 1 $/kg that is considered as the target in order to characterize a fermentation product as platform chemical. The complex nutrient supplements, the raw material market price and the fermentation efficiency were identified as the major reasons for the relatively high MSP observed.

Sunflower-based biorefinery: poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) production from crude glycerol, sunflower meal and levulinic acid.

Polyhydroxybutyrate (PHB) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] production was developed in bioreactor cultures using the strain Cupriavidus necator DSM 7237 cultivated on crude glycerol, sunflower meal (SFM) hydrolysates and levulinic acid as the sole fermentation feedstocks. Bacterial growth and PHB production was influenced significantly by the free amino nitrogen and inorganic phosphorus content of the SFM hydrolysate. Fed-batch bioreactor fermentations led to the production of 27gL(-1) PHB with an intracellular content of 72.9% (w/w). Continuous feeding of levulinic acid led to the production of up to 23.4gL(-1) P(3HB-co-3HV) with an intracellular content of 66.4% (w/w) and a 3HV content of 22.5mol%. A maximum 3HV content of 31mol% was achieved at earlier fermentation time (53h). Thus, levulinic acid could be combined with biodiesel industry by-products for the production of high P(3HB-co-3HV) concentration, intracellular content and industrially useful 3HV content.

Formulation of fermentation media from flour-rich waste streams for microbial lipid production by Lipomyces starkeyi.

Flour-rich waste (FRW) and by-product streams generated by bakery, confectionery and wheat milling plants could be employed as the sole raw materials for generic fermentation media production, suitable for microbial oil synthesis. Wheat milling by-products were used in solid state fermentations (SSF) of Aspergillus awamori for the production of crude enzymes, mainly glucoamylase and protease. Enzyme-rich SSF solids were subsequently employed for hydrolysis of FRW streams into nutrient-rich fermentation media. Batch hydrolytic experiments using FRW concentrations up to 205 g/L resulted in higher than 90% (w/w) starch to glucose conversion yields and 40% (w/w) total Kjeldahl nitrogen to free amino nitrogen conversion yields. Starch to glucose conversion yields of 98.2, 86.1 and 73.4% (w/w) were achieved when initial FRW concentrations of 235, 300 and 350 g/L were employed in fed-batch hydrolytic experiments, respectively. Crude hydrolysates were used as fermentation media in shake flask cultures with the oleaginous yeast Lipomyces starkeyi DSM 70296 reaching a total dry weight of 30.5 g/L with a microbial oil content of 40.4% (w/w), higher than that achieved in synthetic media. Fed-batch bioreactor cultures led to a total dry weight of 109.8 g/L with a microbial oil content of 57.8% (w/w) and productivity of 0.4 g/L/h.

Valorization of industrial waste and by-product streams via fermentation for the production of chemicals and biopolymers.

The transition from a fossil fuel-based economy to a bio-based economy necessitates the exploitation of synergies, scientific innovations and breakthroughs, and step changes in the infrastructure of chemical industry. Sustainable production of chemicals and biopolymers should be dependent entirely on renewable carbon. White biotechnology could provide the necessary tools for the evolution of microbial bioconversion into a key unit operation in future biorefineries. Waste and by-product streams from existing industrial sectors (e.g., food industry, pulp and paper industry, biodiesel and bioethanol production) could be used as renewable resources for both biorefinery development and production of nutrient-complete fermentation feedstocks. This review focuses on the potential of utilizing waste and by-product streams from current industrial activities for the production of chemicals and biopolymers via microbial bioconversion. The first part of this review presents the current status and prospects on fermentative production of important platform chemicals (i.e., selected C2-C6 metabolic products and single cell oil) and biopolymers (i.e., polyhydroxyalkanoates and bacterial cellulose). In the second part, the qualitative and quantitative characteristics of waste and by-product streams from existing industrial sectors are presented. In the third part, the techno-economic aspects of bioconversion processes are critically reviewed. Four case studies showing the potential of case-specific waste and by-product streams for the production of succinic acid and polyhydroxyalkanoates are presented. It is evident that fermentative production of chemicals and biopolymers via refining of waste and by-product streams is a highly important research area with significant prospects for industrial applications.

Process design and optimization of novel wheat-based continuous bioethanol production system.

A novel design of a wheat-based biorefinery for bioethanol production, including wheat milling, gluten extraction as byproduct, fungal submerged fermentation for enzyme production, starch hydrolysis, fungal biomass autolysis for nutrient regeneration, yeast fermentation with recycling integrated with a pervaporation membrane for ethanol concentration, and fuel-grade ethanol purification by pressure swing distillation (PSD), was optimized in continuous mode using the equation-based software General Algebraic Modelling System (GAMS). The novel wheat biorefining strategy could result in a production cost within the range of dollars 0.96-0.50 gal(-1) ethanol (dollars 0.25-0.13 L(-1) ethanol) when the production capacity of the plant is within the range of 10-33.5 million gal y(-1) (37.85-126.8 million L y(-1)). The production of value-added byproducts (e.g., bran-rich pearlings, gluten, pure yeast cells) was identified as a crucial factor for improving the economics of fuel ethanol production from wheat. Integration of yeast fermentation with pervaporation membrane could result in the concentration of ethanol in the fermentation outlet stream (up to 40 mol %). The application of a PSD system that consisted of a low-pressure and a high-pressure column and employing heat integration between the high- and low-pressure columns resulted in reduced operating cost (up to 44%) for fuel-grade ethanol production.

Optimization of batch and fed-batch bioreactors using simulated annealing.

In order for biobased industrial products to compete economically with petroleum-derived products, significant reduction in their processing cost is necessary. Since most bioprocesses are operated in batch or fed-batch mode, their optimization involves theoretical and computational challenges. Simulated annealing (SA), a stochastic optimization algorithm, is used in this study to solve a number of challenging optimization problems related to the design and operation of bioreactors. Two well-known case studies are considered in which the robustness and efficiency of the SA algorithm is demonstrated. More specifically, in the first case study it is shown that the global optimal solution located by SA achieves significant improved productivity when compared with the results of previous investigations. In the second case study a realistic objective function is considered where the economic performance of a bioprocess is optimized. SA exhibits impeccable performance and robustness and was able to locate the global optimal solution irrespective of the initial point selected.