Exopolysaccharides from microalgae: production, characterization, optimization and techno-economic assessment.

Microalgae cultivation for exopolysaccharide production has getting more attention as a result of their high hydrocarbon biosynthesis skill. The aim of this study is to examine the exopolysaccharide production potential of different species of microalgae. In this context, exopolysaccharides were produced from Chlorella minutissima, Chlorella sorokiniana and Botryococcus braunii microalgae and the effects of carbon and nitrogen content in the growth medium and illumination time on exopolysaccharide production were analyzed statistically using Box-Behnken experimental design. In addition, techno-economic assessment of exopolysaccharide production were also performed by using the most productive microalgae and optimum conditions determined in this study. As a result of the experiments, it was seen that C. minutissima, C. sorokiniana and B. braunii produced 0.245 ± 0.0025 g/L, 0.163 ± 0.0016 g/L and 0.117 ± 0.0007 g/L exopolysaccharide, respectively. Statistically, it was observed that there was an inverse relationship between the exopolysaccharide production and investigated parameters such as illumination period and carbon and nitrogen amounts of culture mediums. The techno-economic assessment comprising microalgal exopolysaccharide (EPS) bioprocess was carried out, and it showed that the system can be considered economically viable, yet can be improved with biorefinery approach.

Techno-economic assessment of bioethanol production from lignocellulose by consortium-based consolidated bioprocessing at industrial scale.

Lignocellulose-based biofuels are of major importance to mitigate the impact of international traffic and transport on climate change while sustaining agricultural land for food supply. Highly integrated systems like consolidated bioprocessing (CBP), where enzyme production, enzymatic hydrolysis and fermentation of the released sugars are carried out in one reactor, offer the highest potential to save costs and to make lignocellulose-based biofuels economically competitive. The work described here showed that CBP based on a microbial consortium operated at full-scale (2000 t/d) saves up to 27.5 % of the total ethanol production costs compared to conventional ethanol production from lignocellulose in individual process steps. The cost savings are mainly achieved through lower CAPEX due to less apparatus requirements because of the integrated process, as well as through lower OPEX since no glucose is needed for enzyme production. A comparison with literature estimations of cost savings of CBP based on genetically modified microorganisms results in approximately the same range. As a result of a detailed sensitivity analysis, scale and yield were identified as the main cost-pushers from a process point of view, whereas the price level of the plant location has the highest impact on the investment conditions. In the EU, CBP yields enough margin for profitable production and the possibility to decentralize biomass valorization, whereas in the world's largest ethanol market, the U.S, profitable production of lignocellulosic ethanol can only be achieved by CBP combined with other cost saving techniques, such as utilization of cost-free waste feedstocks, since ethanol has undergone a considerable price slump.

Efficient pullulan production by Aureobasidium pullulans using cost-effective substrates.

In this study, cost-effective substrates such as cassava starch, corn steep liquor (CSL) and soybean meal hydrolysate (SMH) were used for pullulan production by Aureobasidium pullulans CCTCC M 2012259. The medium was optimized using response surface methodology (RSM) and artificial neural network (ANN) approaches, and analysis of variance indicated that the ANN model achieved higher prediction accuracy. The optimal medium predicted by ANN was used to produce high molecular weight pullulan in high yield. SMH substrates increased both biomass and pullulan titer, while CSL substrates maintained higher pullulan molecular weight. Results of kinetic parameters, key enzyme activities and intracellular uridine diphosphate glucose contents revealed the physiological mechanism of changes in pullulan titer and molecular weight using different substrates. Economic analysis of batch pullulan production using different substrates was performed, and the cost of nutrimental materials for CSL and SMH substrates was decreased by 46.1% and 49.9%, respectively, compared to the control using glucose and yeast extract as substrates, which could improve the competitiveness of pullulan against other polysaccharides in industrial applications.

Recent developments in short- and medium-chain- length Polyhydroxyalkanoates: Production, properties, and applications.

Developing renewable resource-based plastics with complete biodegradability and a minimal carbon footprint can open new opportunities to effectively manage the end-of-life plastics waste and achieve a low carbon society. Polyhydroxyalkanoates (PHAs) are biobased and biodegradable thermoplastic polyesters that accumulate in microorganisms (e.g., bacterial, microalgal, and fungal species) as insoluble and inert intracellular inclusion. The PHAs recovery from microorganisms, which typically involves cell lysis, extraction, and purification, provides high molecular weight and purified polyesters that can be compounded and processed using conventional plastics converting equipment. The physio-chemical, thermal, and mechanical properties of the PHAs are comparable to traditional synthetic polymers such as polypropylene and polyethylene. As a result, it has attracted substantial applications interest in packaging, personal care, coatings, agricultural and biomedical uses. However, PHAs have certain performance limitations (e.g. slow crystallization), and substantially more expensive than many other polymers. As such, more research and development is required to enable them for extensive use. This review provides a critical review of the recent progress achieved in PHAs production using different microorganisms, downstream processing, material properties, processing avenues, recycling, aerobic and anaerobic biodegradation, and applications.

Transforming biorefinery designs with 'Plug-In Processes of Lignin' to enable economic waste valorization.

Biological lignin valorization has emerged as a major solution for sustainable and cost-effective biorefineries. However, current biorefineries yield lignin with inadequate fractionation for bioconversion, yet substantial changes of these biorefinery designs to focus on lignin could jeopardize carbohydrate efficiency and increase capital costs. We resolve the dilemma by designing 'plug-in processes of lignin' with the integration of leading pretreatment technologies. Substantial improvement of lignin bioconversion and synergistic enhancement of carbohydrate processing are achieved by solubilizing lignin via lowering molecular weight and increasing hydrophilic groups, addressing the dilemma of lignin- or carbohydrate-first scenarios. The plug-in processes of lignin could enable minimum polyhydroxyalkanoate selling price at as low as $6.18/kg. The results highlight the potential to achieve commercial production of polyhydroxyalkanoates as a co-product of cellulosic ethanol. Here, we show that the plug-in processes of lignin could transform biorefinery design toward sustainability by promoting carbon efficiency and optimizing the total capital cost.

Polyhydroxyalkanoates: Next generation natural biomolecules and a solution for the world's future economy.

Petrochemical plastics have become a cause of pollution for decades and finding alternative plastics that are environmental friendly. Polyhydroxyalkanoate (PHA), a biopolyester produced by microbial cells, has characteristics (biocompatible, biodegradable, non-toxic) that make it appropriate as a biodegradable plastic substance. The different forms of PHA make it suitable to a wide choice of products, from packaging materials to biomedical applications. The major challenge in commercialization of PHA is the cost of manufacturing. There are a lot of factors that could affect the efficiency of a development method. The development of new strategic parameters for better synthesis, including consumption of low cost carbon substrates, genetic modification of PHA-producing strains, and fermentational strategies are discussed. Recently, many efforts have been made to develop a method for the cost-effective production of PHAs. The isolation, analysis as well as characterization of PHAs are significant factors for any developmental process. Due to the biodegradable and biocompatible properties of PHAs, they are majorly used in biomedical applications such as vascular grafting, heart tissue engineering, skin tissue repairing, liver tissue engineering, nerve tissue engineering, bone tissue engineering, cartilage tissue engineering and therapeutic carrier. The emerging and interesting area of research is the development of self-healing biopolymer that could significantly broaden the operational life and protection of the polymeric materials for a broad range of uses. Biodegradable and biocompatible polymers are considered as the green materials in place of petroleum-based plastics in the future.

Energy requirements and economics of acetone-butanol-ethanol (ABE) extractive fermentation: a solvent-based comparative assessment.

The reindustrialization of acetone-butanol-ethanol (ABE) fermentation is hampered by its significant production cost, linked to high product inhibition and low product yield. ABE fermentation can be significantly enhanced by integrating in situ liquid-liquid extraction. In this study, hybrid simulations using Excel® and ASPEN Plus® were performed based on solvent-dependent experimental data (product titer, yield and productivity) to consider the physiological response of the microorganism in specific extractive ABE fermentations, and to quantify the energy requirements and the economic improvement of the overall process. Four scenarios, based on two different solvents (2-butyl-1-octanol, 2B1O, and a vegetable oil, VO) applied in batch or fed-batch operation, were compared with the batch conventional process. Total energy demand decreased in all extractive configurations and the greatest energy savings (61%) were reached with the VO-based fed-batch operation. However, the highest profit increase was achieved with 2B1O in fed-batch mode, reducing the minimum butanol selling price by 29% over the base case, along with 34% savings in raw materials and 80% wastewater reduction. The techno-economical solvent-based comparative evaluation is a useful tool to identify key challenges to be tackled when revisiting ABE extractive fermentation.

Luffa cylindrica Immobilized with Aspergillus terreus QMS-1: an Efficient and Cost-Effective Strategy for the Removal of Congo Red using Stirred Tank Reactor.

Microbial populations within the rhizosphere have been considered as prosperous repositories with respect to bioremediation aptitude. Among various environmental contaminants, effluent from textile industries holds a huge amount of noxious colored materials having high chemical oxygen demand concentrations causing ecological disturbances. The study was aimed to explore the promising mycobiome of rhizospheric soil for the degradation of azo dyes to develop an efficient system for the exclusion of toxic recalcitrants. An effluent sample from the textile industry and soil samples from the rhizospheric region of Musa acuminata and Azadirachta indica were screened for indigenous fungi to decolorize Congo red, a carcinogenic diazo dye, particularly known for its health hazards to the community. To develop a bio-treatment process, Aspergillus terreus QMS-1 was immobilized on pieces of Luffa cylindrica and exploited in stirred tank bioreactor under aerobic and optimized environment. Quantitative estimation of Congo red decolorization was carried out using UV-Visible spectrophotometer. The effects of fungal immobilization and biosorption on the native structure of Luffa cylindrica were evaluated using a scanning electron microscope. A. terreus QMS-1 can remove (92%) of the dye at 100 ppm within 24 h in the presence of 1% glucose and 1% ammonium sulphate at pH 5.0. The operation of the bioreactor in a continuous flow for 12 h with 100 ppm of Congo red dye in simulated textile effluent resulted in 97% decolorization. The stirred tank bioreactor was found to be a dynamic, well maintained, no sludge producing approach for the treatment of textile effluents by A. terreus QMS-1 of the significant potential for decolorization of Congo red.Microbial populations within the rhizosphere have been considered as prosperous repositories with respect to bioremediation aptitude. Among various environmental contaminants, effluent from textile industries holds a huge amount of noxious colored materials having high chemical oxygen demand concentrations causing ecological disturbances. The study was aimed to explore the promising mycobiome of rhizospheric soil for the degradation of azo dyes to develop an efficient system for the exclusion of toxic recalcitrants. An effluent sample from the textile industry and soil samples from the rhizospheric region of Musa acuminata and Azadirachta indica were screened for indigenous fungi to decolorize Congo red, a carcinogenic diazo dye, particularly known for its health hazards to the community. To develop a bio-treatment process, Aspergillus terreus QMS-1 was immobilized on pieces of Luffa cylindrica and exploited in stirred tank bioreactor under aerobic and optimized environment. Quantitative estimation of Congo red decolorization was carried out using UV-Visible spectrophotometer. The effects of fungal immobilization and biosorption on the native structure of Luffa cylindrica were evaluated using a scanning electron microscope. A. terreus QMS-1 can remove (92%) of the dye at 100 ppm within 24 h in the presence of 1% glucose and 1% ammonium sulphate at pH 5.0. The operation of the bioreactor in a continuous flow for 12 h with 100 ppm of Congo red dye in simulated textile effluent resulted in 97% decolorization. The stirred tank bioreactor was found to be a dynamic, well maintained, no sludge producing approach for the treatment of textile effluents by A. terreus QMS-1 of the significant potential for decolorization of Congo red.

Primary purification of intracellular Halomonas salina ectoine using ionic liquids-based aqueous biphasic system.

Ectoine is a zwitterionic amino acid derivative that can be naturally sourced from halophilic microorganisms. The increasing demands of ectoine in various industries have urged the researches on the cost-effective approaches on production of ectoine. Ionic liquids-based aqueous biphasic system (ILABS) was applied to recover Halomonas salina ectoine from cells hydrolysate. The 1-butyl-3-methylimidazolium tetrafluoroborate (Bmim)BF4 was used in the ILABS and the recovery efficiency of ILABS to recover ectoine from H. salina cells lysate was evaluated by determining the effects of phase composition; pHs; crude loading and additional neutral salt (NaCl). The hydrophilic ectoine was targeted to partition to the hydrophilic salt-rich phase. A total yield (YB) of 96.32% ± 1.08 of ectoine was obtained with ILABS of phase composition of 20% (w/w) (Bmim)BF4 and 30% (w/w) sulfate salts; system pH of 5.5 when the 20% (w/w) of crude feedstock was applied to the ILABS. There was no significant enhancement on the ectoine recovery efficiency using the ILABS when NaCl was added, therefore the ILABS composition without the additional neutral salt was recommended for the primary purification of ectoine. Partition coefficient (KE) of 30.80 ± 0.42, purity (PE) of 95.82% and enrichment factor (Ef) of 1.92 were recorded with the optimum (Bmim)BF4/sulfate ILABS. These findings have provided an insight on the feasibility of recovery of intracellular biomolecules using the green solvent-based aqueous system in one single-step operation.

Simultaneous increases in the levels of compatible solutes by cost-effective cultivation of Synechocystis sp. PCC 6803.

Synechocystis sp. PCC 6803, a cyanobacterium widely used for basic research, is often cultivated in a synthetic medium, BG-11, in the presence of 4-(2-hydroxyethyl)-1-piperazine ethanesulfonic acid (HEPES) or 2-[[1,3-dihydroxy-2-(hydroxymethyl)propan-2-yl]amino]ethanesulfonic acid buffer. Owing to the high cost of HEPES buffer (96.9% of the total cost of BG-11 medium), the biotechnological application of BG-11 is limited. In this study, we cultured Synechocystis sp. PCC 6803 cells in BG-11 medium without HEPES buffer and examined the effects on the primary metabolism. Synechocystis sp. PCC 6803 cells could grow in BG-11 medium without HEPES buffer after adjusting for nitrogen sources and light intensity; the production rate reached 0.54 g cell dry weight·L-1 ·day-1 , exceeding that of commercial cyanobacteria and Synechocystis sp. PCC 6803 cells cultivated under other conditions. The exclusion of HEPES buffer markedly altered the metabolites in the central carbon metabolism; particularly, the levels of compatible solutes, such as sucrose, glucosylglycerol, and glutamate were increased. Although the accumulation of sucrose and glucosylglycerol under high salt conditions is antagonistic to each other, these metabolites accumulated simultaneously in cells grown in the cost-effective medium. Because these metabolites are used in industrial feedstocks, our results reveal the importance of medium composition for the production of metabolites using cyanobacteria.

Co-production of DHA and squalene by thraustochytrid from forest biomass.

Omega-3 fatty acids, and specifically docosahexaenoic acid (DHA), are important and essential nutrients for human health. Thraustochytrids are recognised as commercial strains for nutraceuticals production, they are group of marine oleaginous microorganisms capable of co-synthesis of DHA and other valuable carotenoids in their cellular compartment. The present study sought to optimize DHA and squalene production by the thraustochytrid Schizochytrium limacinum SR21. The highest biomass yield (0.46 g/gsubstrate) and lipid productivity (0.239 g/gsubstrate) were observed with 60 g/L of glucose, following cultivation in a bioreactor, with the DHA content to be 67.76% w/wtotal lipids. To reduce costs, cheaper feedstocks and simultaneous production of various value-added products for pharmaceutical or energy use should be attempted. To this end, we replaced pure glucose with organosolv-pretreated spruce hydrolysate and assessed the simultaneous production of DHA and squalene from S. limacinum SR21. After the 72 h of cultivation period in bioreactor, the maximum DHA content was observed to 66.72% w/wtotal lipids that was corresponded to 10.15 g/L of DHA concentration. While the highest DHA productivity was 3.38 ± 0.27 g/L/d and squalene reached a total of 933.72 ± 6.53 mg/L (16.34 ± 1.81 mg/gCDW). In summary, we show that the co-production of DHA and squalene makes S. limacinum SR21 appropriate strain for commercial-scale production of nutraceuticals.

Stress-tolerant non-conventional microbes enable next-generation chemical biosynthesis.

Microbial chemical production is a rapidly growing industry, with much of the growth fueled by advances in synthetic biology. New approaches have enabled rapid strain engineering for the production of various compounds; however, translation to industry is often problematic because native phenotypes of model hosts prevent the design of new low-cost bioprocesses. Here, we argue for a new approach that leverages the native stress-tolerant phenotypes of non-conventional microbes that directly address design challenges from the outset. Growth at high temperature, high salt and solvent concentrations, and low pH can enable cost savings by reducing the energy required for product separation, bioreactor cooling, and maintaining sterile conditions. These phenotypes have the added benefit of allowing for the use of low-cost sugar and water resources. Non-conventional hosts are needed because these phenotypes are polygenic and thus far have proven difficult to recapitulate in the common hosts Escherichia coli and Saccharomyces cerevisiae.

Production of xylanases by Bacillus sp. TC-DT13 in solid state fermentation using bran wheat.

Xylanases have gained increasing importance due to their diverse applications in the food, paper, and pharmaceutical industries, however, the production of these enzymes currently uses expensive substrates. It has already been estimated that more than 30% of the enzyme production cost originates from the substrate. The present study aimed to optimize the production of extracellular xylanases by the Bacillus sp. TC-DT 13 using solid-state fermentation with agro-industrial residues, with a view at reducing the production cost of these enzymes. All the agro-industrial residues were tested in submerged fermentation to select the best inductor to produce xylanase. Among these residues, wheat bran was selected as the best inducer of xylanase production with 1500 U/mL. Regarding solid-state fermentation, the use of wheat bran as the only fermentation substrate was used and a ratio of 1:4 moisture over a time of 144 hours induced higher amount of xylanase reaching 2943 U/g. The use of carbon and nitrogen sources did not result in the increase in production of xylanolitic enzymes. The use of agro-industrial residues in the solid-state fermentation, besides increasing the production of xylanase, reduces the cost of production and is an environmentally friendly alternative.

New sustainable alternatives to reduce the production costs for surfactin 50 years after the discovery.

In 1968, Arima et al. discovered the heptapeptide, known as surfactin, which belongs to a family of lipopeptides. Known for its ability to reduce surface tension, it also has biological activities such as antimicrobial and antiviral. Its non-ribosomal synthesis mechanism was later discovered (1991). Lipopeptides represent an important class of surfactants, which can be applied in many industrial sectors such as food, pharmaceutical, agrochemicals, detergents, and cleaning products. Currently, 75% of the surfactants used in the various industrial sectors are from the petrochemical industry. Nevertheless, there are global current demands (green chemistry concept) to replace the petrochemical products with environmentally friendly products, such as surfactants by biosurfactants. The production biosurfactants still are costly. Thus, an alternative to reduce the production costs is using agro-industrial waste as a culture medium associated with an efficient and scalable purification process. This review puts a light on the agro-industrial residues used to produce surfactin and the techniques used for its recovery.

Heterotrophy as a tool to overcome the long and costly autotrophic scale-up process for large scale production of microalgae.

Industrial scale-up of microalgal cultures is often a protracted step prone to culture collapse and the occurrence of unwanted contaminants. To solve this problem, a two-stage scale-up process was developed - heterotrophically Chlorella vulgaris cells grown in fermenters (1st stage) were used to directly inoculate an outdoor industrial autotrophic microalgal production unit (2nd stage). A preliminary pilot-scale trial revealed that C. vulgaris cells grown heterotrophically adapted readily to outdoor autotrophic growth conditions (1-m3 photobioreactors) without any measurable difference as compared to conventional autotrophic inocula. Biomass concentration of 174.5 g L-1, the highest value ever reported for this microalga, was achieved in a 5-L fermenter during scale-up using the heterotrophic route. Inocula grown in 0.2- and 5-m3 industrial fermenters with mean productivity of 27.54 ± 5.07 and 31.86 ± 2.87 g L-1 d-1, respectively, were later used to seed several outdoor 100-m3 tubular photobioreactors. Overall, all photobioreactor cultures seeded from the heterotrophic route reached standard protein and chlorophyll contents of 52.18 ± 1.30% of DW and 23.98 ± 1.57 mg g-1 DW, respectively. In addition to providing reproducible, high-quality inocula, this two-stage approach led to a 5-fold and 12-fold decrease in scale-up time and occupancy area used for industrial scale-up, respectively.

Biosynthetic strategies to produce xylitol: an economical venture.

Xylitol is a natural five-carbon sugar alcohol with potential for use in food and pharmaceutical industries owing to its insulin-independent metabolic regulation, tooth rehardening, anti-carcinogenic, and anti-inflammatory, as well as osteoporosis and ear infections preventing activities. Chemical and biosynthetic routes using D-xylose, glucose, or biomass hydrolysate as raw materials can produce xylitol. Among these methods, microbial production of xylitol has received significant attention due to its wide substrate availability, easy to operate, and eco-friendly nature, in contrast with high-energy consuming and environmental-polluting chemical method. Though great advances have been made in recent years for the biosynthesis of xylitol from xylose, glucose, and biomass hydrolysate, and the yield and productivity of xylitol are substantially improved by metabolic engineering and optimizing key metabolic pathway parameters, it is still far away from industrial-scale biosynthesis of xylitol. In contrary, the chemical synthesis of xylitol from xylose remains the dominant route. Economic and highly efficient xylitol biosynthetic strategies from an abundantly available raw material (i.e., glucose) by engineered microorganisms are on the hard way to forwarding. However, synthetic biology appears as a novel and promising approach to develop a super yeast strain for industrial production of xylitol from glucose. After a brief overview of chemical-based xylitol production, we critically analyzed and comprehensively summarized the major metabolic strategies used for the enhanced biosynthesis of xylitol in this review. Towards the end, the study is wrapped up with current challenges, concluding remarks, and future prospects for designing an industrial yeast strain for xylitol biosynthesis from glucose.

Biofuel production from straw hydrolysates: current achievements and perspectives.

Straw is an agricultural residue of the production of e.g. cereals, rapeseed or sunflowers. It includes dried stalks, leaves, and empty ears and corncobs, which are separated from the grains during harvest. Straw is a promising lignocellulosic feedstock with a beneficial greenhouse gas balance for the production of biofuels and chemicals. Like all lignocellulosic materials, straw is recalcitrant and requires thermochemical and enzymatic pretreatment to enable access to the three major biopolymers of straw-the polysaccharides cellulose and hemicellulose and the polyaromatic compound lignin. Straw is used for commercial ethanol and biogas production. Considerable research has also been conducted to produce biobutanol, biodiesel and biochemicals from this raw material, but more research is required to establish them on a commercial scale. The major hindrance for launching industrial biofuel and chemicals' production from straw is the high cost necessitated by pretreatment of the material. Improvements of microbial strains, production and extraction technologies, as well as co-production of high-value compounds represent ways of establishing straw as feedstock for the production of biofuels, chemicals and food.

Bioproduction of pure, kilobase-scale single-stranded DNA.

Scalable production of kilobase single-stranded DNA (ssDNA) with sequence control has applications in therapeutics, gene synthesis and sequencing, scaffolded DNA origami, and archival DNA memory storage. Biological production of circular ssDNA (cssDNA) using M13 addresses these needs at low cost. However, one unmet goal is to minimize the essential protein coding regions of the exported DNA while maintaining its infectivity and production purity to produce sequences less than 3,000 nt in length, relevant to therapeutic and materials science applications. Toward this end, synthetic miniphage with inserts of custom sequence and size offers scalable, low-cost synthesis of cssDNA at milligram and higher scales. Here, we optimize growth conditions using an E. coli helper strain combined with a miniphage genome carrying only an f1 origin and a ß-lactamase-encoding (bla) antibiotic resistance gene, enabling isolation of pure cssDNA with a minimum sequence genomic length of 1,676 nt, without requiring additional purification from contaminating DNA. Low-cost scalability of isogenic, custom-length cssDNA is demonstrated for a sequence of 2,520 nt using a bioreactor, purified with low endotoxin levels (<5 E.U./ml). We apply these exonuclease-resistant cssDNAs to the self-assembly of wireframe DNA origami objects and to encode digital information on the miniphage genome for biological amplification.

Simultaneous production of industrially important alkaline xylanase-pectinase enzymes by a bacterium at low cost under solid-state fermentation conditions.

Simultaneous production of alkaline xylanase and all seven types of pectinases by a bacterial isolate, under solid-state fermentation was checked in this study. Under optimized conditions, high concurrent production of xylanase (22,800 ± 578 IU/g substrate) and pectinase (4,832 ± 189 IU/g substrate) was achieved. The different types of pectinases produced were exo-polymethylgalacturonase (782 IU/g), endo-polymethylgalacturonase (6.42 U/g), exo-polygalacturonase (2,250 IU/g), endo-polygalacturonase (11.57 U/g), polymethylgalacturonate lyase (53.99 IU/g), polygalacturonate lyase (59.78 IU/g), and pectin esterase (5.78 IU/g). Wheat bran resulted in the highest titer of both enzymes. The maximum xylanase-pectinase yield was detected after 7 days of incubation with 2 mM MgSO4 and 1.5 g/L K2 HPO4 at wheat bran to moisture ratio 1:1.5 (w/v), media to flask volume ratio 1:25, pH 7.0, temperature 37 °C, and inoculum size 15%. Xylanase was most stable at pH 8.0, retained more than 75% activity up to 24 H, whereas pectinase was most stable at pH 9.0, having full activity even after 24 H. At 45 °C, the xylanase showed 82% residual activity after 6 H of incubation. The pectinase was 97% and 61% stable up to 3 H at 50 and 55 °C, respectively. This is the first report showing the production of xylanase-pectinases by bacterium along with high titer of seven types of pectinases, suitable for industries.

Towards a low CO2 emission building material employing bacterial metabolism (2/2): Prospects for global warming potential reduction in the concrete industry.

The production of concrete is one of the most significant contributors to global greenhouse gas emissions. This work focuses on bio-cementation-based products and their potential to reduce global warming potential (GWP). In particular, we address a proposed bio-cementation method employing bacterial metabolism in a two-step process of limestone dissolution and recrystallisation (BioZEment). A scenario-based techno-economic analysis (TEA) is combined with a life cycle assessment (LCA), a market model and a literature review of consumers' willingness to pay, to compute the expected reduction of global GWP. Based on the LCA, the GWP of 1 ton of BioZEment is found to be 70-83% lower than conventional concrete. In the TEA, three scenarios are investigated: brick, precast and onsite production. The results indicate that brick production may be the easiest way to implement the products, but that due to high cost, the impact on global GWP will be marginal. For precast production the expected 10% higher material cost of BioZEment only produces a marginal increase in total cost. Thus, precast production has the potential to reduce global GWP from concrete production by 0-20%. Significant technological hurdles remain before BioZEment-based products can be used in onsite construction scenarios, but in this scenario, the potential GWP reduction ranges from 1 to 26%. While the potential to reduce global GWP is substantial, significant efforts need to be made both in regard to public acceptance and production methods for this potential to be unlocked.