Fermentation Setup Research Articles

Physico-chemical and functional properties of the lao fermented bamboo shoots (Nor Mai Som) inoculated with potential probiotic bacteria, Pediococcus pentosaceus BBS1 and Lactiplantibacillus plantarum BBS13

Pediococcus pentosaceus BBS1 and Lactiplantibacillus plantarum BBS13 strains were used as starter cultures in Nor mai som fermentation, to determine their physiochemical action, changes in their population, and in reducing cyanide compounds.When BBS1 and BBS13 were added to the fermentation set-ups, the pH values decreased from the initial pH of > 4.6 to pH 3.0 at the end of the fermentation period. The lactic acid levels in all treatments increased from the start of the process through the end of fermentation. During fermentation, lactic acid bacteria (LAB) and total viable count (TVC) populations in all Nor mai som samples showed similar counts of >9 log CFU/g in 24 h of incubation. Thereafter, the counts declined until the completion of the fermentation. Interestingly, Enterobacteriaceae were undetectable in all samples with inoculated starter cultures, whereas their growth in spontaneous fermentation was still found at 3.95 log CFU/g on day 3. Each treatment with the inoculated strains showed cyanide reduction in the range of 62.09 % to 90.31 % at day 10, compared to natural fermentation which registered a reduction of only 49.75 % for the same period. The findings herein indicate that BBS1 and BBS13 when used as starter cultures play a significant role in accelerating the process within 5 days compared to the treatment without inoculation which takes 15 days. BBS1 and BBS13 contribute to the improvement of product quality and may be economically advantageous in large-scale manufacture. This suggests the opportunity to utilize them in various products, including Nor mai som, livestock feeds, and plant-derived fermented products.

Efficient production of polyhydroxybutyrate using lignocellulosic biomass derived from oil palm trunks by the inhibitor-tolerant strain Burkholderia ambifaria E5-3.

Lignocellulosic biomass is a valuable, renewable substrate for the synthesis of polyhydroxybutyrate (PHB), an ecofriendly biopolymer. In this study, bacterial strain E5-3 was isolated from soil in Japan; it was identified as Burkholderia ambifaria strain E5-3 by 16S rRNA gene sequencing. The strain showed optimal growth at 37°C with an initial pH of 9. It demonstrated diverse metabolic ability, processing a broad range of carbon substrates, including xylose, glucose, sucrose, glycerol, cellobiose, and, notably, palm oil. Palm oil induced the highest cellular growth, with a PHB content of 65% wt. The strain exhibited inherent tolerance to potential fermentation inhibitors derived from lignocellulosic hydrolysate, withstanding 3g/L 5-hydroxymethylfurfural and 1.25g/L acetic acid. Employing a fed-batch fermentation strategy with a combination of glucose, xylose, and cellobiose resulted in PHB production 2.7-times that in traditional batch fermentation. The use of oil palm trunk hydrolysate, without inhibitor pretreatment, in a fed-batch fermentation setup led to significant cell growth with a PHB content of 45% wt, equivalent to 10g/L. The physicochemical attributes of xylose-derived PHB produced by strain E5-3 included a molecular weight of 722kDa, a number-average molecular weight of 191kDa, and a polydispersity index of 3.78. The amorphous structure of this PHB displayed a glass transition temperature of 4.59°C, while its crystalline counterpart had a melting point of 171.03°C. This research highlights the potential of lignocellulosic feedstocks, especially oil palm trunk hydrolysate, for PHB production through fed-batch fermentation by B. ambifaria strain E5-3, which has high inhibitor tolerance.

Optimization of Fermentation Conditions for Cellulase Production by Trichoderma harzianum PK5 Obtained from Decaying Palm Kernel Cake

Study’s Novelty/ Excerpt This study successfully optimized cellulase production by Trichoderma harzianum PK5 using the One Factor at a Time (OFAT) approach, identifying copra meal and KNO3 as the best carbon and nitrogen sources. Optimal conditions included a pH of 4.0, 125% moisture concentration, 8% inoculum size, 30°C temperature, and a 7-day incubation period, yielding a high enzyme titre of 252.54±7.73 U/gds in solid-state fermentation. These findings highlight the potential of T. harzianum PK5 as a cost-effective source of cellulases for industrial applications. Full Abstract Cellulases are considered to be among the most important enzymes in the commercial market and in various industries. Their applications are widespread, leading to increased demand and high associated costs. This necessitates the search for more cost-effective cellulases from microorganisms. Therefore, the aim of this study was to optimize cellulase production by Trichoderma harzianum PK5 using the One Factor at a Time (OFAT) approach. The effects of carbon, nitrogen, and various environmental factors were studied in both submerged and solid-state fermentation setups by adjusting one factor at a time based on the optimal conditions established from the previous condition. Copra meal and KNO3 were identified as the best complex carbon and nitrogen sources, respectively, for cellulase production by Trichoderma harzianum PK5. The optimal pH of 4.0, moisture concentration of 125% (v/w), inoculum size of 8%, temperature of 30°C, and an incubation time of 7 days were determined as the optimal conditions for cellulase production by this isolate, resulting in an enzyme titre of 252.54±7.73 U/gds in solid-state fermentation. It was found that cellulase enzyme production by the isolate was constitutive. In conclusion, cellulase production by T. harzianum PK5 was significantly optimized using the OFAT approach

Improving simultaneous saccharification and fermentation by pre-saccharification and high solids operation for bioethanol production from Eucalyptus globulus bark

The European Green Deal emerged as a package of policy initiatives for a green transition, aiming to reach climate neutrality by 2050. Accordingly, the pulp and paper industry has been focused on upgrading residues into value-added products within the forest-based circular economy business model. In this context, this study considered the possibility of using bark, a residue available in high volume on factory floors, for cellulosic ethanol production instead of typical burning for energy generation. Bioconversion of lignocellulosic polysaccharides of bark is a challenge and simultaneous saccharification and fermentation (SSF) setup was chosen to boost cellulosic ethanol production. The introduction of a short pre-saccharification (PS) stage (0, 1 and 4 h) in bioethanol production from Eucalyptus globulus bark, previously submitted to a kraft pretreatment, following an integrated configuration, PS-SSF, at the bioreactor scale improved bioethanol concentration. It was observed that the longer pre-saccharification, the higher productivity. Shifting from this batch PS-SSF (4 h) to a fed-batch PS-SSF (4 h) configuration allowed to increase the solids loading from 8% to 20% (w/v), raising the final bioethanol concentration from 27.4 to 75.9 g L−1, and improving by itself the overall productivity more than 25%. These results show that in the pulp and paper mills, an integrated biorefinery should be considered to foster the total resources use within the circular economy model.

Technology and implementation of fermentative units for bioprotein production from natural gas

Objectives. To conduct a comparative analysis of the features of a fermentation unit design for obtaining bioprotein from natural gas and determine the main technical and structural solutions used in the development of fermentation apparatus, which vary according to the method of organizing hydraulic and mass transfer processes.Results. An analysis of publications devoted to the problem of developing technological equipment for conducting the process of obtaining a bioprotein from natural gas is presented. Using the comparative analysis, the key features of bioreactors and their internal elements are indicated according to the method of organizing the hydrodynamic regime. The main approaches to the technological development of fermentation units for obtaining bioprotein from natural gas are described and technical solutions used in the implementation of these structures are identified.Conclusions. Fermenter designs for the cultivation of methane-oxidizing microorganisms vary according to the main approaches for implementing the hydraulic regime inside the apparatus. While one class of fermentation systems is based on the principle of volumetric mixing in the working space of the apparatus, with the possibility of including external circulation circuits, additional tanks, and auxiliary bioreactors in the system, the other main class relies on the principle of flow (displacement) in the tube space with subsequent release of the gas phase from the circulating culture liquid.

Fermentation of brewer's spent grain liquids to increase shelf life and give an organic acid enhanced ingredient.

Brewer's spent grain (BSG) is an abundant brewing by-product, but a short shelf life limits its use. A rotary drum press can separate BSG into a solid and a liquid fraction (BSG liquid) that contains sugars. Propionic acid producing bacteria (PAB) strains from the family Propionibacteriaceae (DSM 20270, 20272, 20274, 106790) were screened for organic acids formation from BSG liquid in three fermentation setups: A single-step fermentation, a two-step fermentation with Lactiplantibacillus plantarum (NFICC 27) followed by PAB, and a co-culture of PAB with L. plantarum. The two-step fermentation produced 9.5 g/L propionic acid and 5.4 g/L acetic acid. GC-MS analysis of the fermented BSG liquid showed a decrease in off-flavours and an increase in compounds with fruity, chocolate and caramel notes. The fermented BSG liquid also had antimicrobial activity. Fermentation of BSG liquid may therefore be a suitable means of creating a clean label food ingredient with long shelf life.

Effect of microbial fermentation on nutritional and antinutritional contents of cassava leaf

AbstractCassava leaves serves as a source of alternative proteins for people in developing countries who could not easily access the available protein sources. However, its use is limited by the presence of toxic compounds, particularly cyanogenic glycosides. Thus, use of appropriate processing technique is indispensable to reduce the toxic compounds to a safer limit before utilization of cassava leaf. The objective of this study was therefore to evaluate the effect of Lactobacillus plantarum and Saccharomyces cerevisiae strains, and their co‐culture on nutritional contents and antinutritional factors of cassava leaf during fermentation. A 4 × 5 factorial experimental design was used to determine the effect of fermentation setups and time on chemical composition, antinutritional contents, in vitro protein digestibility and mineral contents of cassava leaf. During 48 h of fermentation, a significant change (p < 0.05) in moisture, protein, fiber, fat, and ash contents were observed. Protein content was improved by 34.91%, while in vitro digestibility of protein was improved by 28.07% during 48 h of L. plantarum fermentation. Cyanide, oxalate, tannin, and phytate contents were decreased significantly (p < 0.05) for all fermentation setups. The highest reduction in cyanide (97.17%) and oxalate (86.44%) was achieved under L. plantarum fermentation. The highest reduction in tannin (93.25%) and phytate (91.11%) was achieved under co‐culture fermentation of cassava leaf. A significant (p < 0.05) reduction of mineral contents except iron was observed during 48 h of fermentation. A significant (p < 0.0001) strong negative correlation was found between protein with cyanide (−0.8164), oxalate (−0.7991), phytate (−0.7851), and tannin (−0.6906). In vitro digestibility of protein also showed a strong significant (p < 0.0001) negative correlation with phytate (−0.9628), oxalate (−0.9407), cyanide (−0.9305), and tannin (−0.8493). Application of L. plantarum and S. cerevisiae in cassava leaf fermentation showed significant improvement of nutritional qualities by reducing the antinutritional factors and toxic compounds. Fermentation of cassava leaf using these strains ascertain utilization of cassava leaf for human consumption to tackle protein energy malnutrition.

Mechanisms underlying Clostridium pasteurianum's metabolic shift when grown with Geobacter sulfurreducens.

Recently, a study showed that glycerol fermentation by Clostridium pasteurianum could be metabolically redirected when the electroactive bacterium Geobacter sulfurreducens was added in the culture. It was assumed that this metabolic shift of the fermentative species resulted from an interspecies electron transfer. The aim of this study was to find out the mechanisms used for this interaction and how they affect the metabolism of C. pasteurianum. To get insights into the mechanisms involved, several coculture setups and RNA sequencing with differential expression analysis were performed. As a result, a putative interaction model was proposed: G. sulfurreducens produces cobamide molecules that possibly modify C. pasteurianum metabolic pathway at the key enzyme glycerol dehydratase, and affect its vanadium nitrogenase expression. In addition, the results suggested that G. sulfurreducens' electrons could enter C. pasteurianum through its transmembrane flavin-bound polyferredoxin and cellular cytochrome b5-rubredoxin interplay, putatively reinforcing the metabolic shift. Unravelling the mechanisms behind the interaction between fermentative and electroactive bacteria helps to better understand the role of bacterial interactions in fermentation setups. KEY POINTS: • C. pasteurianum-G. sulfurreducens interaction inducing a metabolic shift is mediated • C. pasteurianum's metabolic shift in coculture might be induced by cobamides • Electrons possibly enter C. pasteurianum through a multiflavin polyferredoxin.

DebaryOmics: an integrative -omics study to understand the halophilic behaviour of Debaryomyces hansenii.

Summary Debaryomyces hansenii is a non‐conventional yeast considered to be a well‐suited option for a number of different industrial bioprocesses. It exhibits a set of beneficial traits (halotolerant, oleaginous, xerotolerant, inhibitory compounds resistant) which translates to a number of advantages for industrial fermentation setups when compared to traditional hosts. Although D. hansenii has been highly studied during the last three decades, especially in regards to its salt‐tolerant character, the molecular mechanisms underlying this natural tolerance should be further investigated in order to broadly use this yeast in biotechnological processes. In this work, we performed a series of chemostat cultivations in controlled bioreactors where D. hansenii (CBS 767) was grown in the presence of either 1M NaCl or KCl and studied the transcriptomic and (phospho)proteomic profiles. Our results show that sodium and potassium trigger different responses at both expression and regulation of protein activity levels and also complemented previous reports pointing to specific cellular processes as key players in halotolerance, moreover providing novel information about the specific genes involved in each process. The phosphoproteomic analysis, the first of this kind ever reported in D. hansenii, also implicated a novel and yet uncharacterized cation transporter in the response to high sodium concentrations.

Effect of solid state fermentation on proximate composition, antinutritional factors and in vitro protein digestibility of maize flour.

Cereals including maize generally have limiting amino acids particularly lysine. In most cases, spontaneous fermentation is used to improve the nutritional profiles of maize‐based products. However, in such fermentation, biological risks including the presence of pathogenic microorganisms, chemical contaminants, and toxic compounds of microbial origin such as mycotoxins pose a health risk. The aim of this study was, therefore, to improve the nutritional properties of maize flour by reducing antinutritional factors through microbial fermentation by strains of Lactobacillus plantarum and Saccharomyces cerevisiae and their cocultures. A factorial experimental design was used to evaluate the effect of fermentation setups and time on proximate composition, antinutritional factors, and in vitro digestibility of proteins in maize flour. During 48 h of fermentation, protein content was improved by 38%, 55%, 49%, and 48%, whereas in vitro protein digestibility improved by 31%, 40%, 36%, and 34% for natural, Lactobacillus plantarum, Saccharomyces cerevisiae, and their coculture‐fermented maize flour, respectively. The highest improvement in protein content and its digestibility was observed for Lactobacillus plantarum strain‐fermented maize flour. Phytate, tannin and trypsin inhibitor activity were reduced significantly (p < .05) for natural, Lactobacillus plantarum, Saccharomyces cerevisiae, and coculture‐fermented maize flour. The highest reduction of phytate (66%), tannin (75%), and trypsin inhibitor (64%) was observed for coculture‐fermented maize flour. The two strains and their cocultures were found feasible for fermentation of maize flour to improve its nutritional profiles more than the conventional fermentation process.

Efficient Production of Pyruvate Using Metabolically Engineered Lactococcus lactis.

Microbial production of commodity chemicals has gained increasing attention and most of the focus has been on reducing the production cost. Selecting a suitable microorganism, which can grow rapidly on cheap feedstocks, is of key importance when developing an economically feasible bioprocess. We chose Lactococcus lactis, a well-characterized lactic acid bacterium, as our microbial host to produce pyruvate, which is a commodity chemical with various important applications. Here we report the engineering of Lactococcus lactis into becoming an efficient microbial platform for producing pyruvate. The strain obtained, FS1076 (MG1363 Δ3ldh Δpta ΔadhE Δals), was able to produce pyruvate as the sole product. Since all the competitive pathways had been knocked out, we achieved growth-coupled production of pyruvate with high yield. More than 80 percent of the carbon flux was directed toward pyruvate, and a final titer of 54.6 g/L was obtained using a fed-batch fermentation setup. By introducing lactose catabolism into FS1076, we obtained the strain FS1080, which was able to generate pyruvate from lactose. We then demonstrated the potential of FS1080 for valorizing lactose contained in dairy side-streams, by achieving a high titer (40.1 g/L) and high yield (78.6%) of pyruvate using residual whey permeate (RWP) as substrate. The results obtained, show that the L. lactis platform is well-suited for transforming lactose in dairy waste into food-grade pyruvate, and the yields obtained are the highest reported in the literature. These results demonstrate that it is possible to achieve sustainable bioconversion of waste products from the dairy industry (RWP) to valuable products.

The Production of Bioethanol from Carob Pods (Ceratonia siliqua L.)

This study seeks to investigate the use of carob (Ceratonia siliqua. L) as a potential source of bioethanol production. In addition, an attempt to optimize the method through sulfuric acid hydrolysis was carried out and the optimum pH range for carob fermentation was studied at pH 2.5, 4.5 and 7.5. Samples of both foreign and locally originating carob were used and any discrepancy in fermentation performance with respect to origin was noted. Each fermentation setup was prepared with 66 gL-1 carob powder, inoculated with 1gL-1 Saccharomyces cerevisiae yeast strain and supplemented with 0.6 mgL-1 thiamine hydrochloride. A total of 36 fermentation broth samples taken at 24-hour time intervals were analysed for different fermentation variables to monitor the progression of fermentation. Changes in total acidity and reducing sugar were analysed through titration techniques and pH. A quantitative sugar profile based on fructose, glucose and sucrose was constructed using an in-house validated method by HPLC-Refractive Index detector. Ethanolic content of the fermentation broth was determined through an in-house validated method by HPLC-UV detector. A significant change (p &lt; 0.05) in ethanol content across time, was detected, with the highest ethanol concentration being achieved in the unhydrolysed control sample with 1.19% v/v from 66gL-1 carob powder.

Consolidated bioprocessing of cellulose to itaconic acid by a co-culture of Trichoderma reesei and Ustilago maydis

BackgroundItaconic acid is a bio-derived platform chemical with uses ranging from polymer synthesis to biofuel production. The efficient conversion of cellulosic waste streams into itaconic acid could thus enable the sustainable production of a variety of substitutes for fossil oil based products. However, the realization of such a process is currently hindered by an expensive conversion of cellulose into fermentable sugars. Here, we present the stepwise development of a fully consolidated bioprocess (CBP), which is capable of directly converting recalcitrant cellulose into itaconic acid without the need for separate cellulose hydrolysis including the application of commercial cellulases. The process is based on a synthetic microbial consortium of the cellulase producer Trichoderma reesei and the itaconic acid producing yeast Ustilago maydis. A method for process monitoring was developed to estimate cellulose consumption, itaconic acid formation as well as the actual itaconic acid production yield online during co-cultivation.ResultsThe efficiency of the process was compared to a simultaneous saccharification and fermentation setup (SSF). Because of the additional substrate consumption of T. reesei in the CBP, the itaconic acid yield was significantly lower in the CBP than in the SSF. In order to increase yield and productivity of itaconic acid in the CBP, the population dynamics was manipulated by varying the inoculation delay between T. reesei and U. maydis. Surprisingly, neither inoculation delay nor inoculation density significantly affected the population development or the CBP performance. Instead, the substrate availability was the most important parameter. U. maydis was only able to grow and to produce itaconic acid when the cellulose concentration and thus, the sugar supply rate, was high. Finally, the metabolic processes during fed-batch CBP were analyzed in depth by online respiration measurements. Thereby, substrate availability was again identified as key factor also controlling itaconic acid yield. In summary, an itaconic acid titer of 34 g/L with a total productivity of up to 0.07 g/L/h and a yield of 0.16 g/g could be reached during fed-batch cultivation.ConclusionThis study demonstrates the feasibility of consortium-based CBP for itaconic acid production and also lays the fundamentals for the development and improvement of similar microbial consortia for cellulose-based organic acid production.

Pseudomonas as Versatile Aromatics Cell Factory.

Aromatics and their derivatives are valuable chemicals with a plethora of important applications and thus play an integral role in modern society. Their current production relies mostly on the exploitation of petroleum resources. Independency from dwindling fossil resources and rising environmental concerns are major driving forces for the transition towards the production of sustainable aromatics from renewable feedstocks or waste streams. Whole-cell biocatalysis is a promising strategy that allows the valorization of highly abundant, low-cost substrates. In the last decades, extensive efforts are undertaken to allow the production of a wide spectrum of different aromatics and derivatives using microbes as biocatalysts. Pseudomonads are intriguing hosts for biocatalysis, as they display unique characteristics beneficial for the production of aromatics, including a distinct tolerance and versatile metabolism. This review highlights biotechnological applications of Pseudomonas as host for the production of aromatics and derived compounds. This includes their de novo biosynthesis from renewable resources, biotransformations in single- and biphasic fermentation setups, metabolic funneling of lignin-derived aromatics, and the upcycling of aromatic monomers from plastic waste streams. Additionally, this review provides insights into unique features of Pseudomonads that make them exceptional hosts for aromatics biotechnology and discusses engineering strategies.

Effect of Isomixing on Grape Must Fermentations of ATF1-Overexpressing Wine Yeast Strains.

Speeding up grape must fermentation would be of great economic benefit. We subjected Saccharomyces cerevisiae VIN13 and two recombinant VIN13-strains expressing ATF1 alleles under two different promoters (either PGK1 or HXT7) to four styles of grape must fermentations; we then assessed the effect of constantly stirring a must fermentation (isomixing). The four different fermentation setups were as follows: isomixed, closed in an ANKOM Rf Gas productions system; isomixed, open in a stirred tall tube cylinder; static, closed constituting a conventional fermentation in a wine bottle equipped with an airlock and static; and static, open in a tall tube cylinder (without stirring). We report on major fermentation parameters and the volatile aroma compositions generated in the finished wines. The primary fermentations of the strains subjected to constant stirring finished after 7 days, whereas the static fermentations reached dryness after 19 days. The wines derived from isomixed fermentations produced approximately 0.7% less ethanol compared to the unstirred fermentations. The speed that the isomixed fermentation took to reach completion may provide an alternative to static fermentations in the preparation of base wines for sparkling wine production. The observed increase of volatiles of isomixed fermentations merits further investigation.

Effect of Acetic Acid on Succinic Acid Production of Fungal Co-culture in Slurry Fermentation

The effect of initial acetic acid concentration on succinic acid production from biologically pretreated birchwood chip-soybean hull mixture using co-culture of Aspergillus niger, Phanerochaete chrysosporium, and Trichoderma reesei in a slurry batch fermentation set-up was investigated. Acetic acid was supplied in various initial concentration: 1.65 g/L, 3.75 g/L, and 5.85 g/L. Low initial acetic acid resulted in decline of succinic acid production which coincided with declining acetic acid concentration. On the other hand, both medium and high initial acetic acid sustained higher succinic acid production with nearly constant acetic acid concentration throughout the five-day slurry batch fermentation. The residual sugar concentration was also observed as this was indirectly affected by the presence of acetic acid in the mixture. The presence of acetic acid in the fermentation media plays a crucial role in the production of succinic acid from a non-conventional source, the fungal co-culture.

A Gram-Scale Limonene Production Process with Engineered Escherichia coli.

Monoterpenes, such as the cyclic terpene limonene, are valuable and important natural products widely used in food, cosmetics, household chemicals, and pharmaceutical applications. The biotechnological production of limonene with microorganisms may complement traditional plant extraction methods. For this purpose, the bioprocess needs to be stable and ought to show high titers and space-time yields. In this study, a limonene production process was developed with metabolically engineered Escherichia coli at the bioreactor scale. Therefore, fed-batch fermentations in minimal medium and in the presence of a non-toxic organic phase were carried out with E. coli BL21 (DE3) pJBEI-6410 harboring the optimized genes for the mevalonate pathway and the limonene synthase from Mentha spicata on a single plasmid. The feasibility of glycerol as the sole carbon source for cell growth and limonene synthesis was examined, and it was applied in an optimized fermentation setup. Titers on a gram-scale of up to 7.3 g·Lorg−1 (corresponding to 3.6 g·L−1 in the aqueous production phase) were achieved with industrially viable space-time yields of 0.15 g·L−1·h−1. These are the highest monoterpene concentrations obtained with a microorganism to date, and these findings provide the basis for the development of an economic and industrially relevant bioprocess.

Statistical Optimisation of Rhamnolipid Production using a Pseudomonas putida Strain Cultivated on Renewable Carbon Sources of Waste Vegetable Oils

Abstract Herein, synthesis of rhamnolipid surfactants was performed using a non-pathogenic Pseudomona s putida strain cultured on a variety of waste frying oils (WFOs) under Taguchi multi-objective optimization design. The effect of substrate types, fermentation setups and incubation time on the biomass concentration, rhamnolipid yield and surface tension of the cultivate media has been investigated. The results demonstrate that the multi-objectives investigation helps to document the optimal limits of the process parameters based on Gray relational analysis. After finding the optimal conditions, a validati on run was performed; therein, the rhamnolipid yield increased from 3.4 to 4.1 g/L; the biomass concentration decreased by 4.84% with an additional surface tension reduction of 2.19% due to an increase of rhamnolipids yield. Overall, soybean WFO was observed to be a preferred substrate for P. putida strain both under Taguchi design and the validation run. The present study proposes a low total of runs and optimum product yield under the Taguchi based multi-objective optimization.

Economic assessment of membrane-based power-to-gas processes for the European biogas market

Four different power-to-gas process chains implementing catalytic methanation and membrane upgrading are presented. Their economics for synthetic natural gas production and hydrogen storage are assessed for the first time in the context of multiple different European gas grid standards by simulation. Influence of two different fermentation setups for biogas production as well as pressure levels from 6 to 15 bar and catalyst specific flow rates from 100 to 150 Nl/(h gCAT) were considered. Based on this simulation an economic analysis was done. Capital expenditures and operational expenditures for electrolysis, methanation, membrane gas upgrading, and compressors of each chain are presented.It is shown that the integration of a simple recycle of the off-gas stream can reduce the costs from up to 2.93 €/Nm³ produced synthetic natural gas to at least 1.63 €/Nm³. Hydrogen storage cost can be decreased from up to 1.81 €/Nm³ stored hydrogen to at least 0.95 €/Nm³. Variation of the fermentation setup only leads to savings in the range of 0.03–0.08 €/Nm³ synthetic natural gas if off-gas recycling is included. Catalyst specific gas flow rate is shown to be of neglectable influence, contributing less than 0.01 €/Nm³ produced synthetic natural gas or stored hydrogen. Pressure influence is more pronounced at up to 0.10 €/Nm³ produced synthetic natural gas and up to 0.05 €/Nm³ stored hydrogen. Optimal operation pressure for simple off-gas recycling is shown to be below 10 bar.

Optimization of cyclopropane fatty acids production in Yarrowia lipolytica.

Cyclopropane fatty acids, which can be simply converted to methylated fatty acids, are good unusual fatty acid candidates for long-term resistance to oxidization and low-temperature fluidity useful for oleochemistry and biofuels. Cyclopropane fatty acids are present in low amounts in plants or bacteria. In order to develop a process for large-scale biolipid production, we expressed 10 cyclopropane fatty acid synthases from various organisms in the oleaginous yeast Yarrowia lipolytica, a model yeast for lipid metabolism and naturally capable of producing large amounts of lipids. The Escherichia coli cyclopropane fatty acid synthase expression in Y.lipolytica allows the production of two classes of cyclopropane fatty acids, a C17:0 cyclopropanated form and a C19:0 cyclopropanated form, whereas others produce only the C17:0 form. Expression optimization and fed-batch fermentation set-up enable us to reach a specific productivity of 0.032g·L-1 ·hr-1 with a genetically modified strain containing cyclopropane fatty acid up to 45% of the total lipid content corresponding to a titre of 2.3±0.2g/L and a yield of 56.2±4.4mg/g.