Fed-batch Mode Research Articles

Limits to biomass productivity during fed-batch cultivation of Laminaria saccharina female gametophyte cells in a stirred-tank photobioreactor

This study compared the growth of Laminaria saccharina female gametophyte filamentous cell suspension cultures in a stirred-tank photobioreactor under batch and fed-batch nutrient addition modes over a 48-day cultivation period. Cultures were grown on GP2 artificial seawater medium (0.75 mM nitrate, N:P = 16:1) at pH 8.3 without iron or copper. Total equivalent nutrient loadings ranged from 0.5X to 9.1X GP2 for batch cultivation and 1.3X to 10.4X GP2 for fed-batch cultivation at delivery rates of 0.0067–0.16 mmol N L−1 day−1 based on nitrate. The multicellular, L. saccharina filamentous clumps were dispersed to nominal size of 100 μm by mechanical blending (~ 16,000 rpm, 5 s) prior to inoculation. Fed-batch addition of all nutrients enhanced biomass productivity by a factor of two over a batch cultivation process at equivalent total nutrient loadings in a stirred-tank photobioreactor. Peak productivity through fed-batch cultivation was 57 mg DCW L−1 day−1, and average final biomass densities exceeded 1800 mg DCW L−1, vs. 30 mg DCW L−1 day−1 and 800–900 mg DCW L−1 for batch cultivation. However, there was a limit to biomass productivity enhancement at cumulative nutrient loadings greater than 3X GP2 that was not the result of insufficient CO2 or light delivery. It is suggested that the formation of large, multicellular clumps approaching 1-mm diameter during stirred-tank cultivation may have ultimately reduced biomass productivity during fed-batch cultivation under nutrient-replete conditions. Therefore, future bioreactor processing strategies might consider mechanical blending to disperse the filament clumps during the cultivation process.

Strategies for improvement of microbial fuel cell performance via stable power generation from real dairy wastewater

The microbial fuel cells (MFCs) are one of the emerging sustainable power sources, that are being effectively used for the simultaneous treatment of wastewater with concomitant generation of electricity. The present study develops a fed-batch process with an optimized level of two microorganisms for concurrent treatment of real dairy wastewater (RDW) and stable power generation using a single-chamber MFC. The MFC exhibits a maximum open circuit voltage of 652 mV at 264 h of fed-batch operation. The unstructured kinetic model suggests that the value of saturation constant (Ks) is 41.67 mg COD/L, indicating mixed culture has a higher affinity towards the utilization of RDW. The fed-batch mode achieves maximum COD removal efficiency of 95.31%, columbic efficiency of 31.58%, a maximum current density of 263 mA/m2, and power density (62.27 mW/m2). The optimum cell voltage and internal resistance of MFC are 0.48 V and 340 Ω, respectively. The study suggests that a fed-batch operation with mixed culture is suitable for the treatment of RDW and able to generate stable power from MFC.

Improvement of laccase biosynthesis by various feeding strategies and in situ integration of biomass separation

In this paper the process of biosynthesis of fungal laccases is addressed with the investigation of methods for improvement of the enzyme’s production efficiency and prolongation of the culture’s performance. The research is focused on improving the biosynthesis results through repeated discontinuous fed-batch cultures, and in situ integration of the process with the first step of downstream processing – biomass separation via specially constructed rotating filter. Four different strategies were applied with varied frequency of feeding and whether the filter was used or not. Based on obtained results, it is claimed that biosynthesis of laccase conducted in repeated discontinuous fed-batch mode provides satisfactory improvement in terms of laccase production per run. The total laccase recovery in the process with daily refills was more than 6 times higher than in the batch mode performed in the same bioreactor.

Sequential fed batch extractive fermentation for enhanced bioethanol production using recycled Spathaspora passalidarum and mixed sugar composition

The simultaneous ethanol production and removal during sequential cell recycle fed batch fermentation provides a complementary route to produce this biofuel from sugar mixtures, which may greatly improve yields and productivity from lignocellulosic hydrolysates. Spathaspora passalidarum is a wild-type strain able to naturally convert glucose, fructose, xylose and arabinose into ethanol. Therefore, the present work has focused on 2G bioethanol production by S. passalidarum aiming at the consumption of all sugars released after pre-treatment and enzymatic hydrolysis of sugarcane bagasse in a single fermentation step. The fermentation strategy with sequential cell recycle, fed-batch mode and ethanol removal in situ was performed on a hemicellulosic hydrolysate medium supplemented with molasses. This strategy gave improved fermentation performance and enabled the co-fermention of all sugars under microaerobic conditions. The maximum ethanol yield and productivity was 0.482 g.g−1 and 9.5 g·L-1·h−1, respectively, showing a process efficiency of 94.3%. The selective ethanol removal enables the operation of the bioreactor at low levels of ethanol (20–30 g·L-1), even with high sugar concentration inputs, accelerating the fermentation performance and avoiding inhibitory effects on yeast metabolism. Applying the cell recycle strategy, S. passalidarum was able to increase its robustness, as shown by a 10-fold increase in ethanol productivity, and it was also able to tolerate a high acetic acid concentration (4.5 g·L-1) during long-term fermentations. These results demonstrate that the bioprocess strategy has a strong potential to improve bioethanol production of rich mixed sugar from lignocellulosic hydrolysates in a single fermentation step.

Influence of heterotrophic and mixotrophic cultivation on growth behaviour of terrestrial cyanobacteria

Terrestrial cyanobacteria are a promising source for the production of biotechnological interesting metabolites. Some of these organisms of potential economic importance live in form of phototrophic biofilms and are therefore difficult to cultivate under laboratory conditions. However, there are some cultivation systems that mimic natural growth conditions, they are neither applicable for a scale-up, nor commercially available. Nevertheless, common cultivation systems like open ponds are designed for submerged conditions and an exchange against emerse photobioreactor systems (ePBRs) would be a cost-intensive procedure. Heterotrophic and mixotrophic cultivation could provide an alternative. In this work, cells of non-axenic mixed cultures of the terrestrial cyanobacteria Trichocoleus sociatus and Nostoc muscorum were cultivated for 14 days under phototrophic, heterotrophic and mixotrophic submerged conditions. The influence of different carbon sources, such as glucose, fructose, galactose, raffinose and potassium acetate, as well as the difference between batch and fed-batch cultivation on growth behaviour was analyzed. Mixotrophic cultivation led to higher cell concentrations as phototrophic and heterotrophic cultivation, regardless of which carbon source was used. A medium supplement of 2.53 g L−1 raffinose yielded a cell dry weight of 3.77 g L−1 for T. sociatus under mixotrophic fed-batch conditions, whereas for N. muscorum the mixotrophic fed-batch mode with glucose was the best option. It led to a dry weight of 2.46 g L−1 after 14 days of cultivation. It was observed that the two strains were able to use several carbohydrates as carbon sources and even much better than acetate. The composition of heterotrophic and mixotrophic non-axenic cultures was analyzed using qPCR during the whole cultivation period. Although there were differences in carbon utilization between the strains, the results indicate that in general terrestrial cyanobacteria are able to grow heterotrophically and that the increase in dry weight is not attributed to the growth of heterotrophic coexisting organisms.

Repetitive Fed-Batch: A Promising Process Mode for Biomanufacturing With E. coli.

Recombinant protein production with Escherichia coli is usually carried out in fed-batch mode in industry. As set-up and cleaning of equipment are time- and cost-intensive, it would be economically and environmentally favorable to reduce the number of these procedures. Switching from fed-batch to continuous biomanufacturing with microbials is not yet applied as these cultivations still suffer from time-dependent variations in productivity. Repetitive fed-batch process technology facilitates critical equipment usage, reduces the environmental fingerprint and potentially increases the overall space-time yield. Surprisingly, studies on repetitive fed-batch processes for recombinant protein production can be found for yeasts only. Knowledge on repetitive fed-batch cultivation technology for recombinant protein production in E. coli is not available until now. In this study, a mixed feed approach, enabling repetitive fed-batch technology for recombinant protein production in E. coli, was developed. Effects of the cultivation mode on the space-time yield for a single-cycle fed-batch, a two-cycle repetitive fed-batch, a three-cycle repetitive fed batch and a chemostat cultivation were investigated. For that purpose, we used two different E. coli strains, expressing a model protein in the cytoplasm or in the periplasm, respectively. Our results demonstrate that a repetitive fed-batch for E. coli leads to a higher space-time yield compared to a single-cycle fed-batch and can potentially outperform continuous biomanufacturing. For the first time, we were able to show that repetitive fed-batch technology is highly suitable for recombinant protein production in E. coli using our mixed feeding approach, as it potentially (i) improves product throughput by using critical equipment to its full capacity and (ii) allows implementation of a more economic process by reducing cleaning and set-up times.

Simultaneous hydrogen production and struvite recovery within a microbial reverse-electrodialysis electrolysis cell

In this research, a novel Microbial reverse-electrodialysis electrolysis struvite-precipitation cell (MRESC) was developed for energy recovery through struvite (MgNH4PO4·6H2O) crystallization and hydrogen production concurrently in a single process without any electrical-grid energy consumption. This hybrid system can effectively transfer the salinity gradient energy to electrical energy as a driving force to produce hydrogen gas coupled with struvite recovery and organic wastewater degradation. A MRESC containing 10 pairs of RED cells, supplied solutions typical of high concentration (600mM NaCl) and low concentration (12mM NaCl) at 1.0mL/min, was operated in the fed-batch mode. The rates of hydrogen production and struvite crystallization were determined to be 0.71m3-H2/m3-Van/d and 7.62g/m2/h, respectively. The gas produced was >92% H2. The Coulombic efficiency was close to or above 100% with a COD removal of 84±6%, and an overall energy efficiency of 28%. The morphology and structure of the main component of accumulated crystal at the cathode were verified by a scanning electron microscope with energy dispersive spectroscopy (SEM-EDS) and X-ray diffraction. These results showed that the MRESC system could be used as an effective bioelectrochemical method for energy recovery in the form of pure hydrogen gas and struvite simultaneously.

Conversion of cardoon crop residues into single cell oils by Lipomyces tetrasporus and Cutaneotrichosporon curvatus: process optimizations to overcome the microbial inhibition of lignocellulosic hydrolysates

In the present work, the production of Single Cell Oils (SCOs) from undetoxified cardoon hydrolysates (UCH) was investigated. The raw material was pretreated by acid catalyzed steam explosion at 195 °C for 7.5 min and hydrolysed at high dry matter content to achieve a final hydrolysate containing 90 g L-1 glucose and 9 g L-1 xylose. The different ability of Cutaneotrichosporon curvatus and Lipomyces tetrasporus to overcome the toxic effect of the biomass degradation by-products, mainly furan derivatives, in different growth phases was investigated in different set-ups conditions including four hydrolysates concentrations, (glucose and xylose respectively 30 + 3, 45 + 4, 60 + 6, and 90 + 9 g L-1) and two fermentation modes, batch and fed batch. The results indicated that the inoculum age corresponded to a different metabolism of the furanic aldehydes only in L. tetrasporus. C. curvatus was severely inhibited by UCH in any growth phase. L. tetrasporus cells in the stationary phase (SP) grew in UCH at any concentration, while cells in the exponential phase (EP) grew only at the highest dilution rate. The maximum lipids yields and lipid cell content of 20% and 47% respectively (7.1 g L-1 lipids) were achieved in batch mode using SP-inocula and the highest dilution ratio. The dominant fatty acid was oleic acid (59%). The scale-up to the 2 L bioreactor, in fed-batch mode, increased the lipids concentration up to 12.7 g L-1 and the productivity up to 0.135 g L-1 h-1.

Fed-batch bioprocess development for astaxanthin production by Xanthophyllomyces dendrorhous based on the utilization of Prosopis sp. pods extract

This work focuses on using renewable sources as feedstock for the microbial production of carotenoids, valuable compounds for various industries. Xanthophyllomyces dendrorhous, which mainly synthesize astaxanthin and β-carotene, was used for the process. We proposed two strategies to achieve high production yields, the correct oxygen supply to the medium and the adoption of a fed-batch mode. Two factors related to the medium's oxygen transfer at a flask scale (working volume and agitation) were evaluated. Astaxanthin production was successfully correlated with the oxygen transfer coefficient (kLa) using a mesquite pods-based medium (MEM) and a chemically defined one (YM). kLa correlations were then used to set the conditions at a reactor scale. An optimum kLa of 16.86 h−1 was adequate to promote astaxanthin production in MEM (1824.13 μg/L). Meanwhile, in YM, optimum production (1656.24 μg/L) was obtained at the highest evaluated levels (17.77 h−1). Thus, a higher oxygen transfer rate is required to produce carotenoids in YM compared with MEM. Astaxanthin production was thus evaluated using a fed-batch process at flask and reactor scales. Reached production levels with fed-batch cultivation were 4465.12 μg/L (flask) and 4130.23 μg/L (reactor). This study demonstrated the correlation between oxygen transfer and carotenoids' production and the potential utilization of mesquite feedstock in a fed-batch bioprocess to improve carotenoids' yield by X. dendrorhous.

P450Jα: A New, Robust and α‐Selective Fatty Acid Hydroxylase Displaying Unexpected 1‐Alkene Formation

Oxyfunctionalization of fatty acids (FAs) is a key step in the design of novel synthetic pathways for biobased/biodegradable polymers, surfactants and fuels. Here, we show the isolation and characterization of a robust FA α-hydroxylase (P450Jα ) which catalyses the selective conversion of a broad range of FAs (C6:0-C16:0) and oleic acid (C18:1) with H2 O2 as oxidant. Under optimized reaction conditions P450Jα yields α-hydroxy acids all with >95 % regioselectivity, high specific activity (up to 15.2 U mg-1 ) and efficient coupling of oxidant to product (up to 85 %). Lauric acid (C12:0) turned out to be an excellent substrate with respect to productivity (TON=394 min-1 ). On preparative scale, conversion of C12:0 reached 83 % (0.9 g L-1 ) when supplementing H2 O2 in fed-batch mode. Under similar conditions P450Jα allowed further the first biocatalytic α-hydroxylation of oleic acid (88 % conversion on 100 mL scale) at high selectivity and in good yields (1.1 g L-1 ; 79 % isolated yield). Unexpectedly, P450Jα displayed also 1-alkene formation from shorter chain FAs (≤C10:0) showing that oxidative decarboxylation is more widely distributed across this enzyme family than reported previously.

Genome-scale metabolic rewiring improves titers rates and yields of the non-native product indigoidine at scale

High titer, rate, yield (TRY), and scalability are challenging metrics to achieve due to trade-offs between carbon use for growth and production. To achieve these metrics, we take the minimal cut set (MCS) approach that predicts metabolic reactions for elimination to couple metabolite production strongly with growth. We compute MCS solution-sets for a non-native product indigoidine, a sustainable pigment, in Pseudomonas putida KT2440, an emerging industrial microbe. From the 63 solution-sets, our omics guided process identifies one experimentally feasible solution requiring 14 simultaneous reaction interventions. We implement a total of 14 genes knockdowns using multiplex-CRISPRi. MCS-based solution shifts production from stationary to exponential phase. We achieve 25.6 g/L, 0.22 g/l/h, and ~50% maximum theoretical yield (0.33 g indigoidine/g glucose). These phenotypes are maintained from batch to fed-batch mode, and across scales (100-ml shake flasks, 250-ml ambr®, and 2-L bioreactors).

Growing Spirulina (Arthrospira platensis) in seawater supplemented with digestate: Trade-offs between increased salinity, nutrient and light availability

Utilization of digestate as a source of nutrients must be understood in the context of their effects on light penetration. These conflicting consequences of digestate utilization were verified by growing the cyanobacterium Arthrospira platensis (Spirulina) in artificial seawater supplemented with 2.5 %, 5%, 10 % or 15 % (v/v) of anaerobically digested effluents (digestate) in a fed-batch mode. Therefore, the study investigates the impact of the complex interactions between nutrient availability, increased salinity, which affects negatively the photosynthetic efficiency of A. platensis and variable turbidities associated with the variable ranges of digestate additions. At the lowest digestate concentration growth was hindered by low nutrient availability. Biomass production was highest at 5% digestate (≈1300 mg/L dry biomass) but further increases in digestate concentrations lowered biomass accumulation (≈1020−1150 mg/L dry biomass). On the other hand, greater concentrations of digestate and thus more nutrients, led to greater protein content (44–55 % in higher concentrations versus 22−30% in the lowest), while A. platensis cells had enhanced photosynthetic performances. The latter is likely due to the fact that addition of digestate reduced light intensity and therefore reduced the negative effect of salinity on the photosynthetic apparatus. The balance between nutrient and light availability, as associated with variable digestate rates, may be managed towards the production of A. platensis biomass with variable qualitative and quantitative biochemical parameters.

Enhanced production of poly(3-hydroxybutyrate-co-3-hydroxyvalerate) biopolymer by recombinant Bacillus megaterium in fed-batch bioreactors.

Polyhydroxyalkanoates (PHAs) are biodegradable polyesters accumulated in a wide variety of microorganisms as intracellular carbon and energy storage compounds. Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) (PHBV) is one of the most valuable biopolymers because of its superior mechanical properties. Here, we developed a bioprocess utilizing recombinant Bacillus megaterium strain for PHBV over-production from glucose, without any precursor addition. PHA production was performed in a controlled bioreactor by batch and fed-batch modes using wild-type B. megaterium and rec-B. megaterium cells overexpressing the native phaC gene. The effect of oxygen transfer rate on biomass formation and PHA accumulation was also investigated, under different dissolved oxygen levels. Structural and thermal properties of PHA were characterized by GC-FID, 1H-NMR, TGA and DSC analyses. Significantly, the copolymer produced from glucose as the carbon source in rec-B. megaterium was composed of 58mol% of 3-hydroxyvalerate monomers. After 66h, rec-B. megaterium cells in fed-batch fermentation with a pre-determined growth rate µ0 = 0.1h-1 produced the highest CDW (7.7g L-1) and PHA concentration (6.1g L-1). Moreover, an exponential glucose feeding profile resulted in 2.2-fold increase in PHA yield compared to batch cultivation. Overall, this study paves the way to an enhanced biopolymer production process in B. megaterium cells, where the highest product yield on cell was obtained as YP/X = 0.8gg-1.

Description of a Decentralized Small Scale Digester for Treating Organic Wastes

This manuscript deals with the detailed design of a small digestion prototype intended as a commercial unit fully operational to cover the demand for decentralized treatment of wastes. These plants are highly affected by the complex nature of wastes giving rise to different operating problems that should be considered in detail. This paper describes the design and start-up strategy of a small-scale digestion plant with a volume of 8 m3 designed to operate with a hydrolysis pretreatment unit. The plant was designed to treat fruit and vegetable wastes as substrates derived from a local processing food factory. The performance of the plant during fed-batch operation was reported. The strategy of inoculating the reactor only to a third of its original volume and subsequently increasing the volume of the reactor by using the fed-batch mode was inadequate. The acid pH of the feeding substrate resulted in the application of a low organic loading rate with a volumetric variation of just 19.7 L/d. The performance of the plant was evaluated at non-steady state conditions and resulted in excessive destruction of volatile solids due to the low nitrogen content of the feeding substrate. The prototype reported a specific methane production of 232 L/kg volatile solids despite the low feeding rate supplemented.

Giving credit to residual bioresources: From municipal solid waste hydrolysate and waste plum juice to poly (3-hydroxybutyrate)

Municipal solid waste (MSW) is massively generated all over the world. Its organic fraction (OFMSW), which represents a high percentage of MSW, mainly contains biodegradable materials, namely food waste, paper and garden waste. The social cost of OFMSW treatment and/or disposal is a serious and widespread problem, particularly in highly populated areas. Thus, effective and innovative solutions, which include the upgrading of OFMSW, are being currently sought. In fact, the OFMSW abundance, availability and average composition suggest its considerable potential within the circular economy desideratum, paving the way to valorisation approaches. In this context, an OFMSW sugar-rich hydrolysate and its validation as a substrate for the production of the polyester poly(3-hydroxybutyrate) (P(3HB)), to date the only bioplastic easily biodegradable in marine environment, were successfully obtained in a previous study. Based on those results, this work addresses the upscaling of the fermentative production, in fed-batch mode, of P(3HB) by Burkholderia sacchari. The OFMSW hydrolysate was used as cultivation medium due to its balanced nutrient composition, while a plum waste juice, also rich in sugars, was applied as feed to the bioreactor. By implementing this strategy, a maximum P(3HB) production of 30 g·L−1 with an accumulation of 43% g (P(3HB))/g cell dry weight (CDW) after 51 h, was achieved. The use of the hydrolysate as initial medium resulted in higher CDW (71 g·L−1) than that of the simulated hydrolysate (62 g·L−1 in average), probably because the OFMSW hydrolysate favours biomass growth in detriment of P(3HB) production.

Conversion of Exhausted Sugar Beet Pulp into Fermentable Sugars from a Biorefinery Approach

In this study, the production of a hydrolysate rich in fermentable sugars, which could be used as a generic microbial culture medium, was carried out by using exhausted sugar beet pulp pellets (ESBPPs) as raw material. For this purpose, the hydrolysis was performed through the direct addition of the fermented ESBPPs obtained by fungal solid-state fermentation (SSF) as an enzyme source. By directly using this fermented solid, the stages for enzyme extraction and purification were avoided. The effects of temperature, fermented to fresh solid ratio, supplementation of fermented ESBPP with commercial cellulase, and the use of high-solid fed-batch enzymatic hydrolysis were studied to obtain the maximum reducing sugar (RS) concentration and productivity. The highest RS concentration and productivity, 127.3 g·L−1 and 24.3 g·L−1·h−1 respectively, were obtained at 50 °C and with an initial supplementation of 2.17 U of Celluclast® per gram of dried solid in fed-batch mode. This process was carried out with a liquid to solid ratio of 4.3 mL·g−1 solid, by adding 15 g of fermented solid and 13.75 g of fresh solid at the beginning of the hydrolysis, and then the same amount of fresh solid 3 times every 2.5 h. By this procedure, ESBPP can be used to produce a generic microbial feedstock, which contains a high concentration of monosaccharides.

Plasmid DNA Production in Proteome-Reduced Escherichia coli.

The design of optimal cell factories requires engineering resource allocation for maximizing product synthesis. A recently developed method to maximize the saving in cell resources released 0.5% of the proteome of Escherichia coli by deleting only three transcription factors. We assessed the capacity for plasmid DNA (pDNA) production in the proteome-reduced strain in a mineral medium, lysogeny, and terrific broths. In all three cases, the pDNA yield from biomass was between 33 and 53% higher in the proteome-reduced than in its wild type strain. When cultured in fed-batch mode in shake-flask, the proteome-reduced strain produced 74.8 mg L−1 pDNA, which was four times greater than its wild-type strain. Nevertheless, the pDNA supercoiled fraction was less than 60% in all cases. Deletion of recA increased the pDNA yields in the wild type, but not in the proteome-reduced strain. Furthermore, recA mutants produced a higher fraction of supercoiled pDNA, compared to their parents. These results show that the novel proteome reduction approach is a promising starting point for the design of improved pDNA production hosts.

The effect of sialic acid content in glycans on thrombolytic activity of tissue plasminogen activators

Purpose: to investigate the dependence of the thrombolytic activity of tissue plasminogen activators (tPA) alteplase and tenecteplase on the degree of sialylation of the oligosaccharide component of molecules. Materials and methods: tPA specimens with an average degree of sialylation were obtained by cultivating CHO clones-producers in the fed-batch mode; desialylated forms of tPA were obtained by processing with neuraminidase, and hypersialylated forms of tPA were obtained by cultivating clones-producers in a medium with the addition of butyrate. The content of sialic acids was determined by resorcinol method, and the activity of tPA was determined by fibrin clot lysis. Results: the dependence of tenecteplase activity on the content of sialic acids in the molecule is demonstrated. The activity of tenecteplase falls below the limits of the target range when the content of sialic acids is more than 5 residues per tenecteplase molecule. No such relation was found for alteplase. Conclusion: the content of sialic acid residues affects the biological activity of tenecteplase; the activity of alteplase does not depend on the degree of sialylation of the molecule.

Evaluating the performance of coupled MFC-MEC with graphite felt/MWCNTs polyscale electrode in landfill leachate treatment, and bioelectricity and biogas production.

A bioelectricity producing system was configured by connecting to a microbial electrolysis cell producing hydrogen, in which both systems were without mediator, to treatment the landfill leachate of the and generate bioelectricity and hydrogen. The anode electrode was made with MWCNTs polyscale coating on graphite felt and the cathode electrode with activated carbon coating on carbon cloth. In the MFC-MEC coupled system, the electrodes were connected in series using copper wire. The system was set up in a fed-batch mode and the landfill synthetic leachate was injected into the anode MFC-MEC chamber as fuel. In MFC, the highest voltage, current density and power density were 1114mV, 44.2A/m3 and 49.24W/m3, respectively. The maximum of the coulombic efficiency system was 94.10%. The highest removed COD, NH4-N and P was 97.38%, 79.56% and 74.61%, respectively. In the MEC, the maximum of voltage input, current density and power density was 1106mV, 43.88 A/m3and 48.54W/m3, respectively. The maximum coulombic efficiency system was 125.54%. Also the highest removed COD, NH4-N and P was 97.46%, 78.81% and 76.25%, respectively. The highest biogas production rate and its yield were 39mL/L.d, and 0.0118L/g CODrem, respectively. This study found that the MFC-MEC coupled system had promising potential for strong wastewaters treatment, such as the leachate of landfill; and the in-site use of generated electricity and the production of useful fuels such as biogas.

Fed-batch polyhydroxybutyrate production by Paraburkholderia sacchari from a ternary mixture of glucose, xylose and arabinose.

Polyhydroxybutyrate (PHB) is a biodegradable bioplastic that is comparable with many petroleum-based plastics in terms of mechanical properties and is highly biocompatible. Lignocellulosic biomass conversion into PHB can increase profit and add sustainability. Glucose, xylose and arabinose are the main monomer sugars derived from upstream lignocellulosic biomass processing. The sugar mixture ratios may vary greatly depending on the pretreatment and enzymatic hydrolysis conditions. Paraburkholderia sacchari DSM 17165 is a bacterium strain that can convert all three sugars into PHB. In this study, fed-batch mode was applied to produce PHB on three sugar mixtures (glucose:xylose:arabinose = 4:2:1, 2:2:1, 1:2:1). The highest PHB concentration produced was 67g/L for 4:2:1 mixture at 41h corresponding to an accumulation of 77% of cell dry weight as PHB. Corresponding sugar conversion efficiency and productivity were 0.33g PHB/g sugar consumed and 1.6g/L/h, respectively. The results provide references for process control to maximize PHB production from real sugar streams derived from corn fibre.