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Continuous mashing provides advantages compared to conventional batch-wise mashing in terms of space time yield. The majority of fermentable sugars are generated during the so-called “β-amylase rest” (62–64 °C). These low molecular sugars are fermented later in the brewing process by yeasts and therefore determine the beer attenuation degree. Biological malt variations complicate the application of a continuous system in industrial scale particularly concerning targeted quality parameters. The aim is the prediction of sugar formation from process parameters for a real time control system. Therefore, a semi-empirical model for sugar formation in a continuous stirred tank reactor (CSTR) system was developed under incorporation of the residence time distribution (RTD). The here presented model, which focuses on the “β-amylase rest”, is able to predict fermentable sugar concentrations in the continuous “β-amylase rest” with sufficient accuracy, in contrast to models that only use the flow rate and the reactor volume to determine the reaction time. However, the precision and trueness depend on the quality of the empirical data acquired previously in laboratory experiments for the selected temperature and raw material quality.

Biohydrogen (H2) is considered to be a significant contributor to sustainable economy. However, due to current yields and production rates, large-scale technical implementation of biological H2 production is still a long way off. In this study, two highly productive H2 producers, Enterobacter aerogenes and Clostridium acetobutylicum, were synergistically combined in an artificial microbial consortium (co-culture) for H2 production. Moreover, this co-culture was utilized in a bioelectrochemical system referred to as microbial electrolysis cell, where a small voltage (0.8 V) is applied to enforce H2 production. The experiments were conducted in closed batch mode using cellobiose as carbon source. Each of the applied approaches (co-culture and applied voltage) led to an increase in H2 evolution rate (HER), resulting in a maximum HER of 0.93 mmol L−1 h−1 for the co-culture at an applied voltage of 0.8 V. With the further scale-up and optimization of the examined system parameters, sustainable H2 production for large-scale applications might be feasible within the near future.

Hydrolysis of biomass (e.g. bagasse) leads to xylose as one of the primary sugars for fermentation to bioethanol, along with glucose. The selection of a suitable microorganism and consequently selection of suitable aeration levels for the selected microorganism plays a significant role in xylose conversion. This work focuses on the kinetics of bioethanol production from xylose using Pichia stipitis with the development of a MATLAB mathematical model (based on the combined Andrews and Levenspiel's model with oxygen limitation and inhibition terms included), considering the effects of substrate, oxygen, biomass and product concentrations on sugar utilisation, growth rate and ethanol formation. Experiments were carried out to validate the kinetic model under anaerobic and microaerobic growth conditions in a batch process. The results showed good correlation with an average R2 of 0.92 for bioethanol production, 0.95 for xylose consumption and 0.83 for biomass growth. Different aeration levels of 0.0, 0.1 and 0.2 vvm and different initial biomass concentrations of 0.3, 1.5 and 3 g L-1 were tested, in which the combination of aeration at 0.1 vvm and a biomass concentration of 3 g L-1 resulted in the highest ethanol yield and productivity of 0.45 g g-1 and 0.75 g L-1 h-1 respectively.

A novel aeration strategy has been developed at lab and bench-scale for Bacillus thuringiensis (Bt) derived biopesticides production through solid-state fermentation, using a mixture of digestate and biowaste as substrates. A Box-Behnken design was performed to select key parameters of the spore production process, being temperature and biodegradability the factors with a significant effect. Further tests confirmed the importance of oxygen content for spore production. Thus, a two-stage aeration strategy consisting of a microaeration phase followed by a high-rate aeration period was developed and tested. The production strategy was validated in a 22-L reactor using two different strains (Bt kusrtaki, Btk, and israelensis, Bti), demonstrating the robustness of the protocol. Maximum production of 1.3 × 108 spores g-1 dry matter for Btk and 4 × 108 spores g-1 dry matter for Bti were obtained, representing a final yield of 5 and 29 spores produced per initial CFU, respectively.

Ammonia-rich lagoon supernatant has a low alkalinity/nitrogen ratio, which is ideal for single reactor nitritation-denitritation operation. In the present study, an integrated fixed film and activated sludge system in sequencing batch mode (IFAS-SBR) was operated at 21 °C for 140 days. The stability and feasibility of nitritation-denitritation performance was evaluated, and the microbial activities and microbial community dynamics were investigated. With a hydraulic retention time (HRT) of 2 days, the IFAS-SBR achieved a stable inorganic nitrogen removal rate of 98 %. Nitritation and denitritation activities were both higher in suspended flocs as compared to biofilm. The dominant nitrifying and primary denitrifying genera were Nitrosomonas and Thauera, respectively. During long-term operation, the relative richness of Nitrosomonas and Thauera increased in both biofilm (from 0.27 % to 1.12 % and from

Chemical pesticides cause serious problems to the environment, as well as human and animal health. A conceptual design and economic analysis was carried out for a hypothetical factory in order to produce an environmentally friendly insect controller agent from Azadirachta indica cell culture. The proposed factory is composed of a series of bioreactors that can produce 60.0 kg of active compound/batch. This designed plant had a capacity of 136 batches/year, which represents 40,800 kg of bioinsecticide, and it was located in Medellin (Colombia) with a total building cost of 12.2 million USD. Three bioinsecticide formulations, two equipment costs and variation in product/substrate yields were analyzed. To achieve profitability in the project, the minimum selling price of the formulated products was calculated between 76.9–330.0 USD/kg (Net Present Value > 0). This is the first report of a bioprocess factory design and economic analysis for an insect controller agent using plant cell culture.

Polyethylene terephthalate (PET) is a major contributor to plastic pollution due to its widespread presence in synthetic fibres. As an intermediate in the chemical recycling of PET, disodium terephthalate (Na2TA) can be harnessed as a cheap microbial substrate for the cultivation of Pseudomonas sp. GO16. Here, we present the model-based optimisation of a liquid feeding regime with the purpose of improving the automation and operational ease of Na2TA conversion into Pseudomonas sp. GO16 biomass. The model was parameterised and validated using data from dynamic liquid-phase and solid-phase feeding experiments. The validated model identified sodium ion accumulation as a key determinant of bioprocess performance and was used to design a liquid-phase feeding strategy that maximises Pseudomonas sp. GO16 biomass synthesis. The obtained biomass concentrations of 10.5 g/L (liquid-phase feeding) and 15.3 g/L (solid-phase feeding) are the highest ever reported using Na2TA as a sole carbon source for microbial growth.

Recently, bacterial quorum quenching (QQ) has been proven as a novel approach for biofouling mitigation in membrane bioreactors (MBRs). The information about microbial community is vital for the development of QQ strategies. Also, the change of microbial community may affect the biofouling propensity of sludge. In this study, the effects of exogenous QQ on microbial community dynamics in MBRs were investigated, along with biofouling propensity of activated sludge. QQ MBR dosed with exogenous QQ bacteria exhibited a better anti-biofouling, whereas the wastewater treatment performance was almost no difference compared with control MBR. As for the microbial community, exogenous QQ had an impact on both the bacterial diversities and community composition, especially for the quorum sensing (QS) and QQ bacteria in situ. The addition of exogenous QQ could reduce the QQ ability of sludge itself in the short term, and enhance its biofouling propensity. These findings provided new insights for the development of QQ strategies.

A quantitative analytical method to determine the dead cell ratio of bacteria (death ratio) in sludge was developed for evaluating technologies and determining a sufficient amount of ozone for the sludge ozone process. The method with SYTO9 and propidium iodide as staining agents for live and dead cells, respectively, was optimized. The death ratio developed in this study could successfully predict the reduction ratio of the excess sludge in the sludge ozone process with different ozone dosages. Consequently, the death ratio was proven to be a suitable indicator for excess sludge reduction.

In this study, anaerobic membrane bioreactor (AnMBR) was applied for the treatment of a model slurry of high-strength organic solid waste. Continuous monitoring of reactor performances by chemical analyses and fine-scale tracing of the AnMBR sludge microbiome by high-throughput 16S rRNA gene sequencing were conducted during the long-term operation with increased organic loading rates (OLRs) up to 5.26 kgCOD m−3 day−1. Stable treatment was achieved at the highest OLR for over 170 days. The chemical oxygen demand removal rate of around 99%, membrane flux of 3.31 ± 0.40 L m−2 h−1, and biogas production rate of 31.1 ± 4.8 L day−1 were observed. The latter two parameters were improved after the sludge retention time (SRT) control, showing 4.76 ± 0.25 L m−2 h−1 and 34.5 ± 6.9 L day−1, respectively. The principal coordinate and taxonomic analyses of the sequence data showed that the sludge microbiome was changed drastically in response to both the OLR increase and SRT control. The species-level characterization showed that the relative abundances of aceticlastic methanogens, e.g., Methanosaeta concilii, decreased at high OLRs, whereas those of hydrogenotrophic methanogens, such as Methanolinea mesophila, as well as a syntrophic bacterium Smithella propionica, increased under the high OLRs and SRT control conditions. These results strongly suggest that the effective treatment of the high-strength organic solid waste slurry was mediated via the syntrophic methanogenesis pathway in the AnMBR.

Agro industrial residues, cheap sources of energy have high potential in the area of fermentation for the production of lignocellulases. Different agro industrial waste products were evaluated as substrates in submerged and solid-state fermentation for xylanolytic enzyme production by Bacillus pumilus and the enzyme titers were compared. Higher titer of endoxylanase was obtained with solid state than with liquid fermentation with feeble amount of cellulase. High proteolytic activity was observed in submerged fermentation where as in solid state the proteolytic activity was lower in all cases except in media supplemented with soy meal due to its high protein content. The endoxylanase produced by solid-state fermentation was stable over a wide range of pH and temperatures. The highest enzyme activity was obtained at pH 6.5–7 and at 50 °C. The enzyme could retain 30% of its activity even after 1 h at 60 °C. Considering the conditions under which Kraft pulps are bleached during the manufacture of paper, xylanase from B. pumilus exhibit favorable potential for application in the paper processing industries.

The objectives of this study were to culture a more stable denitrification granular sludge and to investigate the effects of hydraulic shear force on the stability of the granular sludge. The stability consists of shear stability and removal stability, which are characterized by the shear sensitivity (Kss) and by the relative standard deviation of the specific nitrogen removal rate for three consecutive days (RSD-N3), respectively. Two upflow granular sludge blanket (USB) reactors under different hydraulic shear conditions were used to culture granular sludge. The Kss of the mature granular sludge in USBH (G = 24.7 s−1) and USBL (G = 14.5 s−1) were 0.000024 and 0.0051, respectively. The USBH only required 56 days to obtain mature granular sludge, whereas the USBL required 70 days. These results indicated that higher hydraulic shear tended to shorten the granulation time and enhance the shear stability of the granular sludge. The RSD-N3 of the USBL during the maturation period was only 3.68%, which is approximately 32.84% of the value for the USBH, indicating better removal stability for the nitrogen with the USBL. SEM indicated bacillus bacteria were the largest component of the granular microbial community, and metagenomics using high-throughput sequencing identified Methyloversatilis and Azospira as the dominant microorganisms. These findings are important for the development of technologies in this field and have extensive applications in the denitrification of granular sludge.

WOS: 000367776500012, In this study, fungal membrane bioreactor (FMBR) and semiconductor photocatalytic membrane reactor (PMR) were used in order to test the efficiency of integrated fungal biodegradation and photocatalytic degradation of textile wastewater from reactive washing processes. It was found that color removal and chemical oxygen demand (COD) reduction efficiencies were 88% and 53% for photocatalytic degradation, respectively. TiO2 and ZnO were tested as semiconductor catalysts in the PMR and TiO2 showed better efficiencies than ZnO for both color and COD removal. However, it was attained that color removal and COD reduction efficiencies were about 56% and 60% for fungal biodegradation using Phatterochaete chrysosporium, respectively. Moreover, integrated system in which photocatalytic degradation was employed as a post-treatment application after fungal biodegradation process achieved high removal efficiencies for color and COD removal as 93% and 99%, respectively. (C) 2015 Elsevier B.V. All rights reserved., Scientific and Technological Research Council of Turkey (TUBITAK) [113Y334], This work was funded by The Scientific and Technological Research Council of Turkey (TUBITAK), Project No: 113Y334.

The influence of mixing on microorganism integrity and product formation is a critical design parameter for solid-state fermentation bioreactors. The effects of intermittent mechanical mixing on the solid-state fermentation of wet corn distillers grain with Trichoderma reesei NRRL 11460 for the production of cellulase were investigated. Experiments were conducted using the unbuffered media at mixing frequencies of 0, 1, 2, 3, and 6 d −1 at 27.5 °C with an initial moisture content of 50%. The results indicate that mixing caused about a tenfold increase in spore production compared to fermentations at static conditions. The cellulase enzyme activity produced was minimally affected by mixing with only a 5–10% decrease in filter paper activity for mechanically mixed fermentations compared to static fermentations. Mixing at lower frequencies of 1, 2, and 3 d −1 caused an increase in CO 2 evolution compared to static conditions and higher mixing frequencies of 6 d −1 . A correlation between substrate weight loss and cumulative CO 2 evolution was established. The ability to intermittently mix a solid-state fermentation bioreactor with minimal detrimental effects increases the feasibility of onsite production of enzymes at biofuel facilities to lower the overall production costs of cellulosic biofuels.

Biofuels are suitable alternatives to conventional and fossil fuels that pose serious environmental adverse effects to society. Bioethanol is the most promising biofuel and can be generated from lignocellulosic biomasses. Forest residues are outside the human food chain and inexpensive raw materials, but they need a previous pretreatment, in order to improve the cellulose accessibility for further bioconversion. The study of bioethanol production from rockrose pretreated by steam explosion (SE) was carried out employing separate enzymatic hydrolysis and fermentation (SHF) or simultaneous saccharification and fermentation (SSF) approaches. Saccharification of untreated rockrose attained only 0.9% of sugars yield. However, the steam explosion pretreatment promoted the disruption of interfibrillar surfaces of fibers with partial degradation of lignin thus enhancing the accessibility of polysaccharides toward enzymatic hydrolysis. Alkaline extraction after steam explosion pretreatment of rockrose residue (R-SE-OH) led to the partial removal of lignin, hemicelluloses, and other degradation products from fibre surface allowing an increase of 75% in the glucose yield. Bioethanol production in SSF mode was faster and slightly more efficient process than SHE providing the best results: ethanol concentration of 16.1 g L-1, fermentation efficiency of 69.8% and a yield of 22.1 g ethanol/100 g R-SE-OH. (C) 2015 Elsevier B.V. All rights reserved.

Microbial screening and culture optimization is a laborious, multifaceted and expensive procedure often taking years and millions to identify the ideal strain for specific use. In this study, a high throughput, tablet-sized, low cost photobioreactor, herein referred as “PhotoBiobox”, was fabricated and tested for screening and culture optimization of microalgae suitable for biomass and biodiesel production, and CO2 sequestration. PhotoBiobox is equipped with a LED array and photo gradient filter offering different light intensities. PhotoBiobox was fabricated to screen and cultivate several microbial strains in 96-well plate in wide temperature range and CO2 atmosphere. To test its efficacy, a total of 12 microalgal strains were isolated from Korean freshwaters, identified and screened for high growth and lipid accumulation potential. Among the 12 strains, Parachlorella sp., JD076 showed highest growth rate, remarkable stability and tolerance to different temperature regimes. Optimization experiments using PhotoBiobox revealed that this strain had optimum temperature range and light intensity of 24–25 °C and 400 μmol m−2 s−1, respectively, with high growth rate and lipid content in 5% CO2 condition. The screening and optimization of culture conditions using PhotoBiobox took just 15 days, in total, which could radically reduce both screening costs and time. PhotoBiobox can be used as a screening and optimization reactor in several areas of microbiology and cell biology, while serving as a prototype for furthering research on miniaturization in this field.

Fungal delignification can be considered as a feasible process to pre-treat lignocellulosic biomass in biofuel production, if its performance is improved in terms of efficiency thorough a few modifications. In this study, Trichoderma viride was utilized to investigate the effect of wet-milling, addition of surfactant (Tween 80) and optimization of operating factors such as temperature, biomass to liquid medium ratio and glucose concentration on biodelignification of rice straw. Next, the enzymatic hydrolysis of pretreated biomass was studied at various pretreatment times. Results revealed that the wet milling and addition of surfactant increases the lignin removal about 15% and 11%, respectively. The optimization of operating factors resulted in high lignin removal efficiency equal to 74% in a 30 day pretreatment. The maximum enzymatic saccharification of pretreated biomass at optimum conditions was obtained equal to 56%. Conversion of cellulose to reducing sugars during the pretreatment stage was 21% which suggests that higher saccharification efficiency could be achieved in a simultaneous pretreatment and saccharification process.

Simultaneous methanogenesis and short-cut denitrification processes have attracted attention because it enables the removal of organic matter and nitrogen in a same reactor. In this study, these processes were applied to the treatment of blue mussels, which are discharged worldwide intermittently and in vast quantities as organic solid waste. The effects of substrate COD/NO2−-N ratios on denitrifying and methanogenic performances were evaluated in batch experiments. NO2− acclimated sludge was used as a part of seed sludge to enhance the tolerance to NO2−. Two acclimated sludges were obtained by two-different acclimating conditions which exposed to influent COD/NO2−-N ratios of 25 with high COD loading rate and 5 with low COD loading rate during acclimation periods (referred to as AS25 and AS5). AS25 added reactors showed the relatively high methanogenic and denitrifying performances compared to AS5 added reactors. The results obtained in AS25 added reactors showed comparable results to different studies which used liquid substrates. High COD and NO2− removal efficiencies were achieved under substrate COD/NO2−-N ratio ranging from 8.6 to 123, representing the successful performance for the treatment of blue mussels which contains COD/N ratio of 16.3 in their tissue.

A suspended biofilter, as a new bioreactor, was constructed for removal of VOCs (volatile organic compounds). The biofilter bed (height of 30 cm, diameter 16 cm and working volume of 6.0 L) was formed by applying suspended carrier with porous surface and the carrier itself has a density slightly lower than water. According to the results, it was found that the suspended biofilter was suitable to treat the toluene-contaminated stream. Since it could startup quickly, tolerate great transient shock loadings, and possess average removal efficiency higher than 90.2% in a toluene loading range of 11.0–58.5 g m −3 h −1 . What is more, it also gained a maximum elimination capacity of 113.6 g m −3 h −1 at a toluene loading rate of 272.2 g m −3 h −1 . The remarkable performance could be contributed to the rich bacterial communities for toluene degradation. A following 16S rRNA gene sequence analysis reveals that the communities contain high efficient toluene-degrading bacteria, i.e., Acinetobacter sp. Tol 5, Burkholderia , and Comamonadaceae . In addition, after a long-term operation of 141 days, no clogging was observed although there was a high biomass concentration in the biofilter bed. It demonstrated that this novel suspended biofilter overcome clogging and accumulation of biomass, which are the drawback of fixed biofilter.

This work aims at the characterization and the biorefinery of Hesperaloe funifera by means of the use of its three main components: separating hemicellulose by hydrothermal treatments; cellulose pulp by various pulping processes (soda, soda–anthraquinone, ethanolamine, ethyleneglycol, diethanolamine and diethyleneglycol); and exploitation of pulping liquor, rich in lignin, by pyrolysis and gasification processes. The contents in lignin, α-cellulose, holocellulose, hemicellulose, ethanol–benzene extractives, hot water solubles, 1% NaOH solubles and ash of H. funifera were found to be 7.3%, 40.9%, 76.5%, 35.6%, 4.0%, 13.5%, 29.5% and 5.9%, respectively. The mean fibre length, 4.19 mm, exceeds those for some non-wood materials. By using sulfuric acid in the hydrothermal treatment (170 °C, 0, 20 min after reaching operating temperature, 8 liquid/solid ratio, and 0.3% sulfuric acid), gives a liquid fraction containing 4.62% of glucose, 10.56% of xylose, 1.28% of arabinose, and a solid fraction with a solid yield of 57.0%. The best pulp of Hesperaloe pulp was obtained by cooking with 10% NaOH and 1% anthraquinone at 155 °C for 30 min, exhibited good values of yield (48.3%), viscosity (737 mL/g), Kappa number (15.2), tensile index (83.6 Nm/g), stretch (3.8%), burst index (7.34 kN/g) and tear index (3.20 mNm2/g). Moreover, the soda–anthraquinone pulps of raw material are better than the pulps from solid fraction of hydrothermal treatments. Finally, acidification (pH 6) of soda–anthraquinone pulping liquor was carried out to separate lignin-rich solids, by which pyrolysis gave a gas containing 1.13% H2, 31.79% CO and 1.86% CH4 by weight. Gasification of the same sample provided a gas containing 0.18% H2, 24.50% CO and 17.75% CH4.

In order to overcome scale-up limitations of conventional tray-type solid-state fermentation (SSF) bioreactors, a cylindrical fixed-bed bioreactor with forced aeration was investigated for the production of a pool of industrially relevant enzymes by Aspergillus awamori IOC-3914 using babassu cake as raw material. Significant internal radial and axial temperature gradients were observed (up to 2.4 °C cm−1), but despite of this, good titers of the production of the six enzyme groups evaluated was observed in all three bed layers sampled. Maximum activities of exoamylases, endoamylases, proteases, xylanases and cellulases (CMCase) were, respectively, 73.4, 55.7, 31.8, 23.8 and 6.2 U g−1. Moreover, a considerable production of isoamylases (27.0 U g−1) was observed, although the production of starch-debranching enzymes by SSF is rarely reported. Productivities were highest for endoamylases (0.95 U g−1 h−1) and exoamylases (0.67 U g−1 h−1). The present results show that despite considerable axial and radial temperature gradients, significant levels of different enzymes can be obtained, giving evidence that fixed-bed bioreactors with forced aeration present a promising alternative in terms of instrumented bioreactors for SSF processes.

To solve clogging-related issues after the long-term operation of a fungi-based bio-trickling filter (BTF) which started with Fusarium oxysporum, an in-depth analysis on the mechanisms of four △P control methods, including biological, nutrient control, physical and stagnation methods, were investigated. The biological control method showed superior performance compared to other approaches. It reduced the △P from 1000 Pa to 100 Pa within one week, and remained the △P at this level for two months, with maintained removal efficiency (RE) of nearly 100%. The average RE during the high △P period was 88.6%, and a maximum toluene elimination capacity of 125.4 g m−3 h-1 was achieved at an empty bed residence time of 27 s. This study is the first comparison of these four pressure-reducing techniques in a fungi-based BTF, and obtained an effective biological control method, which is of great value for the further industrial application of the BTFs.

Eco-friendly, cost efficient and effective extraction methods have become significant for the industries applying zero waste principles. the two main objectives of this study were; to examine fucoxanthin extraction from wet Phaeodactylum tricornutum using subcritical fluid extraction and to characterize the residual biomass in order to determine the potential application areas. the highest fucoxanthin yield of 0.69 +/- 0.05 mg/g wet cell weight was achieved using methanol with solvent-to-solid ratio of 200:1 at 120 rpm, 20 MPa pressure and at 35 degrees C for 60 min by subcritical extraction. Microscopy images showed that most of the cells were disrupted and intracellular components were effectively released. Based on the results of energy dispersive spectroscopy, biomass contained a mixture of organic molecules including mainly carbon (57-72%), oxygen (26-41%), magnesium (0.6-1.4%) and silica (0.4-1%) (wt%). These results make the residual biomass a potential candidate for various areas such as bioenergy, material sciences and sensor technologies., Scientific and Technological Research Council of Turkey (TUBITAK) as a part of Cost ActionTurkiye Bilimsel ve Teknolojik Arastirma Kurumu (TUBITAK) [115M014, ES1408], This study was supported by the Scientific and Technological Research Council of Turkey (TUBITAK) with the project number of 115M014 as a part of Cost Action ES1408.

Although various methods have been developed for microalgae harvesting, problems such as chemical toxicity, low efficacy, low flexibility, and high cost, still remain with the current methods. In the present study, an effective biological separation method has been developed to harvest microalgae via immobilization on exogenous fungal mycelium. Fungal mycelium was added into microalgae culture and air mixed for the immobilization. The immobilized microalgae with fungal mycelium were naturally precipitated within 10 min after stopping the mixing. Both marine (e.g. Nannochloropsis sp.) and freshwater (e.g. Chlorella vulguris) microalgae were almost completely (94–97%) precipitated using the mycelium of Aspergillus nomius CCK-PDA 7#6. The precipitated mixed biomass was separated by simple filtration using sieve. A 70% initial nutrients supplement to de-algated culture medium gave high growth yield (0.43 g/l) in subsequent microalgae cultivation. The mycelium can be obtained free or at low-cost as waste from a fungal fermentation process of producing valuable products. The developed method is, therefore, very promising for economical harvesting of microalgae.

Recently, it has been reported that the aerobic/extended-idle (AEI) regime can achieve a satisfied biological phosphorus removal (BPR). Although the AEI regime has exhibited some merits, its main drawback that the extended-idle phase (e.g., 210–450 min) is much longer than the anaerobic phase (e.g., 60–120 min) performed in the aerobic/oxic (A/O) regime requires to be addressed. In this study, a new configuration of sequencing batch reactor (SBR) with sludge tank halved (STH-SBR) was therefore designed. After stable operation, 96.9 ± 0.5% of total phosphorus was removed in the STH-SBR, which was higher than that in the AEI-SBR (86.9 ± 0.8%) and A/O-SBR (84.7 ± 1.3%). Further investigations showed that the biomass cultured in the STH-SBR contained more polyphosphate accumulating organisms but less glycogen accumulating organisms than that in the AEI-SBR and A/O-SBR. In the STH-SBR, the aerobic glycogen accumulation was lower than that in the A/O-SBR while the average idle phosphorus release was greater than that in the AEI-SBR. Finally, the key enzyme activities in the AEI and A/O regimes were compared for the first time, and the reasons for the AEI regime showing lower exopolyphosphatase and polyphosphate kinase activities were also discussed.

Microbial fuel cells are attracting attention as one of the systems for producing electrical energy from organic compounds. We used commercial baker's yeast (Saccharomyces cerevisiae) for a glucose fuel cell because the yeast is a safe organism and relatively high power can be generated in the system. In the present study, a milliliter (mL)-scale dual-chamber fuel cell was constructed for evaluating the power generated by a variety of yeasts and their mutants, and the optimum conditions for high performance were investigated. When carbon fiber bundles were used as an electrode in the fuel cell, high volumetric power density was obtained. The maximum power produced per volume of anode solution was 850 W/m3 under optimum conditions. Furthermore, the power was examined using seven kinds of yeast. In Kluyveromyces marxianus, not only the power but also the power per consumed glucose was high. Moreover, it was suggested that xylose is available as fuel for the fuel cell. The fuel cell powered by K. marxianus may prove to be helpful for the effective utilization of woody biomass.

The aim of this study was to investigate the possibility of using microalgae as an oxygen supplier for nitrification. In order to measure oxygen demands of nitrification, the activated sludge were cultured in a selective medium for 150 days, and enriched nitrifying biomass was successfully obtained. The enriched nitrifiers were used to estimate oxygen demands for nitrification and used for co-culturing with microalgae. Oxygen transfer rates (OTR) were also measured for various mixing conditions to determine if mixing without forced aeration could satisfy oxygen demands of nitrification. For all mixing conditions, OTR were lower than the oxygen uptake rates (OUR) of nitrifiers. As a result, nitrification without forced aeration was incomplete due to oxygen deficiency. Meanwhile, oxygen production rates (OPR) of 6 microalgae species were measured, and it was demonstrated that C. vulgaris, S quadricauda, D. communism and C. emersonii could supply sufficient oxygen for nitrification at all mixing modes. Based on these results, 4 species of microalgae with sufficient oxygen supplying capabilities were selected for co-culturing with enriched nitrifiers, and full nitrification was accomplished without forced aeration. Finally, the electric energy of co-culture was estimated and showed that energy consumption by co-culture was lower than that of aerated nitrifiers.

Turning microplastic litter into reusable products is a resource-saving and eco-friendly strategy of disposing of plastic pollution. This work realized a value-added insight of reusing microplastic waste by processing the recycled microplastic items with clay waste into composite particle (CP). Furthermore, the systematic evaluation of CP particle was carried out in a Liquid-solid fluidized bed bioreactor (LSFBBR-CP) treating septic sewage with low COD to nitrogen ratio (C/N ≤3). The commercial inorganic particle, bioceramsite (BC), was tested in the LSFBBR-BC for comparison. During the 257-day stepwise operation, two LSFBBRs constantly achieved effluent of TCOD Y o b s ≤0.067 g VSS g-1 COD). Comparatively, the lower fluidization velocity for the CP particles ( u l , 0.67-1.20 cm s-1) not only contributed to high biomass attachment (17.2 mg VSS g-1 CP particles) but also favored nitrifiers (Nitrosomonas, Nitrosospira, Nitrobacter and Nitrospira) enrichment. Additionally, the LSFBBR-CP outperformed the LSFBBR-BC in energy conservation by consuming 41.1–47.4% less energy for fluidization, due to the lower u l . Contrary to BC particles’ attrition regarding to particle size decrease and surface chemicals loss, the CP particles exhibited superiority in physio-chemical stability. Those comparative advantages confirmed that the CP could be a promising alternative for BC as a carrier particle in LSFBBR, suggesting that turning microplastic litter into reusable carrier particle for FBBRs is feasible.

Waste oil is an economical alternative carbon resource in Yarrowia-based erythritol production, but the water insolubility limits its further utilization. Loofah sponge (LS), a natural polymer material and accessible agricultural waste, was selected as oil-in-water dispersant in this study. In the oil–erythritol cultivation system with LS addition, efficient oil dispersion and enhanced erythritol production (by ˜30%) were achieved, with high biomass and scarce residual oil in the medium. Up to 60.0 g/L of waste oil could be completely consumed under the effect of LS, resulting to an erythritol yield of 0.76 ± 0.03 g/g oil. Scanning electron microscopy (SEM) images and reusability experiments showed that the LS fiber was well preserved and could be stable for more than five continuous cycles in this process. The changes in activities of the metabolic enzymes suggested an enhanced carbon flux in erythritol synthesis pathway, which was accompanied with an improved oxygen consumption. Moreover, with LS addition, scale-up and fed-batch cultivations was well conducted, up to 114.3 ± 1.8 g/L of erythritol was produced from waste oil when the two cultivation strategies were combined. This study demonstrated an efficient and eco-friendly method for the utilization of waste oily substrates in production of microbial metabolites.

The potential of using sorghum milling waste for the development of a biorefining strategy for the production of bioethanol was investigated. Both red and white sorghum were processed using a traditional Nigerian wet-milling process to sorghum flour. The sorghum milling waste, sorghum bran, was hydrolysed using both enzymatic and dilute acid hydrolysis to produce a generable fermentation feedstock. The hydrolysates were subsequently investigated for fermentative biofuel production. Following a hydrolysis step, a medium containing ˜61 g/L glucose was obtained. Trace presence of inhibitors was detected in the hydrolysates and sufficient nitrogen content to support microorganism growth and bioethanol production. In test bioethanol production experiments using the sorghum milling waste derived hydrolysates only, 24.35 g/L bioethanol was produced by a yeast Kluyveromyces marxianus, equivalent to a yield of 0.15 g bioethanol per g of sorghum milling waste.

New polyoxometalate–laccase integrated system (PLIDS) employing polyoxometalate [SiW 11 V V O 40 ] 5− and laccase of Trametes versicolor for the continuous delignification of eucalypt kraft pulp has been developed. Pulp was delignified in a batch reactor containing catalytic amounts of [SiW 11 V V O 40 ] 5− at about 90 °C under atmospheric pressure. Re-oxidation of reduced polyoxometalate (POM) with laccase was carried out at 45 °C in a separate aerated bioreactor coupled with an ultrafiltration tubular ceramic membrane. This allowed the separation of laccase from re-oxidized POM, which was supplied in turn continuously to the delignification reactor. Proposed PLIDS allowed sustainable pulp delignification with minimal degradation of polysaccharides. The implementation of PLIDS, instead the fist chlorine dioxide stage (D) in conventional DEDED bleaching sequence, showed almost 60% of chlorine dioxide savings with strength properties of the bleached pulp (90% ISO) similar to those obtained after the conventional bleaching.

Converting microalgae oil into biodiesel is considered a promising route in the field of biofuel production. However, the cost of microalgae-based biodiesel is still too high to be economically feasible. The high cost of microalgae-based biodiesel is mainly a result of downstream processing, in particular from the extraction of oil out of the microalgal biomass. This study proposes a bacterial (enzymatic) destruction pretreatment of the microalgae cell wall to render the microalgal oil extraction more efficient. It has been found that the cell wall of microalgae can be modified if the microalgal biomass is co-cultured with an indigenous bacterial isolate Flammeovirga yaeyamensis in a salt concentration of 3% and a pH of 8.0. Following this treatment, the activities of some hydrolytic enzymes (i.e., amylase, cellulases, and xylanase) have been detected in the co-culture of F. yaeyamensis and the oil-rich microalga (Chlorella vulgaris ESP-1). The SEM micrographs clearly show specific damage to the microalgae cell wall caused by the bacterial treatment. We found that when the microalgae is pretreated with a concentrated co-culture supernatant (containing the hydrolytic enzymes), a nearly 100% increase in lipid extraction efficiency is obtained. The proposed bacterial disruption method seems to be an effective and environmentally friendly way of improving the efficiency of oil extraction and biofuel production from a microalgal biomass.

Chlorella vulgaris was cultivated in two different 2.0 L-helicoidal and horizontal photobioreactors at 5 klux using the bicarbonate contained in the medium and ambient air as the main CO2 sources. The influence of bicarbonate concentration on biomass growth as well as lipid content and profile was first investigated in shake flasks, where the stationary phase was achieved in about one half the time required by the control. The best NaHCO3 concentration (0.2 g L−1) was then used in both photobioreactors. While the fed-batch run performed in the helicoidal photobioreactor provided the best result in terms of biomass productivity, which was (84.8 mg L−1 d−1) about 2.5-fold that of the batch run, the horizontal configuration ensured the highest lipid productivity (10.3 mg L−1 d−1) because of a higher lipid content of biomass (22.8%). These preliminary results suggest that the photobioreactor configuration is a key factor either for the growth or the composition of this microalga. The lipid quality of C. vulgaris biomass grown in both photobioreactors is expected to meet the standards for biodiesel, especially in the case of the helicoidal configuration, provided that further efforts will be made to optimize the conditions for its production as a biodiesel source.

Models of bioprocesses conducted in bioreactors play a crucial role in the analysis, design, control and development of these bioprocesses. The present work developed a mathematical model for Trametes versicolor dye decolorization and enzymatic production in a fluidized bed bioreactor operating in batch, repeated batch and continuous mode. The mathematical model considers all of the steps involved in a dye decoloration process, such as the initial dye adsorption on the biomass, intracellular degradation, extracellular degradation, enzyme production and enzyme excretion to the broth. Results obtained from specific experiments at different experimental conditions were used to estimate the kinetic constants. Finally, the whole mathematical model was constructed and validated. Although the variability of the measures, the model predicts the tendency of the experimental results which supports the reliability of the established model and shows that the model can be used to successfully simulate dye decoloration and enzyme production in a fluidized bioreactor.

To maintain long-term lignin-degrading enzyme production under non-sterile conditions was a key to the technical application of white rot fungi in wastewater treatment. In this work, a novel open fungal reactor system with ozone as the bactericide, and using immobilized Phanerochaete chrysosporium, was built and operated continuously to produce the manganese peroxidase and decolorize the Acid Blue 45. The results showed that an average of 84% Acid Blue 45 decolorization, the manganese peroxidase production with its activity ranging from 63 U L−1 to 5 U L−1, was achieved during about 25 days system continuous operation. The contaminating bacteria in the reactor can be controlled at a level of 4.65 × 104 CFU ml−1 that did not adversely affect the fungal activity. The result of this study provides a new practical way for future design and operation of white-rot fungi reactor under non-sterile conditions.

In our previous work, the ability of laccase enzymes to improve the fermentation performance of the thermotolerant yeast Kluyveromyces marxianus CECT 10875 on steam-exploded wheat straw slurry was demonstrated. As a continuation of this study, the present research evaluates different aspects, including pretreatment conditions, process configurations and substrate loadings, with the aim to proceed towards the use of K. marxianus and laccases for second generation ethanol production. For it, two wheat straw slurries resulting from different steam explosion pretreatment conditions (200. °C, 2.5. min and 220. °C, 2.5. min) were employed at various substrate loadings [5-14% (w/v)] under two process configurations SSF (simultaneous saccharification and fermentation) and PSSF (presaccharification and simultaneous saccharification and fermentation). The better performance of K. marxianus was observed on the slurry produced at softer conditions. Its lower inhibitors content allowed to increase the total solids loading up to 10% (w/v) in both process configurations, reaching higher ethanol concentrations (12. g/L). Moreover, laccase detoxification improved these results, particularly in SSF processes, increasing the substrate loading up to 12% (w/v) and, consequently, obtaining the highest ethanol concentration (16.7. g/L). © 2013 Elsevier B.V.

A newly built 200-L-pilot plant was used for testing a novel chemo-enzymatic process for producing fine flax fibers without the weather-associated risks of dew retting. Raw, green and decorticated flax fibers were placed inside trays in the tempered main tank of the pilot plant, where a vertically acting mechanism gently moved the parallel fiber bundles. The fibers were incubated in an alkaline bath, in a pectinolytic culture of Geobacillus thermoglucosidasius PB94A and in a peroxide-softener bath. Finally the fibers were dried, combed and hackled into a sliver that is ready for wet-spinning of linen yarns. A total of 140 kg of raw fibers were treated in 40 different experiments in the pilot plant. The resolution of the raw fibers improved from 7.3 to 2.7 ± 0.3 after the treatment. The fineness was enhanced from 37.4 dtex to 11.1 ± 1.2 dtex. The proposed pilot-plant process produced constant-quality fibers and could be easily up-scaled.

A baffled reactor with repeated coupling of aerobic and anaerobic conditions (rCAA) was constructed and the mechanism of the on-site sludge reduction was analyzed systematically. During the long-term operation of 3 years, the chemical oxygen demand (COD) removal efficiency reached over 90% on average and the sludge yield in the rCAA system was 0.098 kg suspended sludge (SS) kg(-1) COD, which was approximately 36.3% of that in a conventional activated sludge process at an influent COD of 700-800 mg L-1 and hydraulic retention time (HRT) of 15 h. Analysis of soluble components, sludge characteristics, microorganism community and metabolic activities in the rCAA system showed that, when the sludge in the aerobic zone flowed into the anaerobic zone, sludge destruction and degradation occurred. Intracellular organic substances were then released and further hydrolyzed to small molecular compounds. These intermediate substances were degraded in subsequent aerobic compartments. In this way, cryptic growth of the sludge was realized that could contribute to sludge reduction. Microbial ecological analysis by denaturing gradient gel electrophoresis (DGGE) further showed that the rCAA process spatially domesticated the different microbial communities along the flow direction of the bioreactor, which enhanced excess sludge lysis and transformation, cryptic growth and bacterial predation. (C) 2012 Elsevier B.V. All rights reserved.

The use of the completely autotrophic nitrogen removal over nitrite (CANON) process as a post-treatment for nitrogen removal from anaerobically pre-treated swine slurry is studied in the present work. The ammonium removal, under oxygen-limited conditions, in a system with anammox bacteria mainly in the form of granules and aerobic ammonium oxidizing bacteria mainly as dispersed biomass was researched in an air pulsing sequencing batch reactor operated at room temperature. The achieved nitrogen removal rate was of 0.46 kg N/(m3 d) treating 300 mg NH4+-N/L with values of nitrogen removal efficiencies around 75%. The presence of slowly or non-biodegradable organic matter (from 260 to 45 mg COD/L) did not affect the operation of the process. By means of the FISH technique, Nitrosomonas were detected as the majority of ammonia oxidizing bacteria in the sample, and Candidatus “Brocadia fulgida” and Candidatus “Brocadia anammoxidans” as the anammox bacteria. The comparison of this aerobic process with other post-treatments for effluents from anaerobic digesters showed that the CANON process is a promising alternative to remove nitrogen from effluents generated in pig farms.

This study presents the sono-assisted pretreatment and enzymatic saccharification of sugarcane bagasse (SCB) for the production of bioethanol. The effect of sono-assisted alkali (NaOH) pretreatment on the removal of hemicellulose and lignin from SCB was studied and the results showed 80.8% of hemicellulose and 90.6% of lignin removal. Sono-assisted enzymatic saccharification was performed with Cellulomonas flavigena (MTCC 7450) and the yield was found to be affected by liquid-to-solid ratio (LSR), cell mass and pH. The optimum reaction time, LSR, cell mass and pH were found to be 360 min, 15:1, 15 g/L and 6.0 respectively. At optimum conditions, the maximum glucose yield obtained was 91.28% of the theoretical yield and the maximum amount of glucose obtained was 38.4 g/L. The enhancement in performance may be correlated with the swelling of cellulose and accelerated enzymatic saccharification due to the application of ultrasound. The hydrolyzate obtained was fermented using Zymomonas mobilis (MTCC 89) and about 91.22% of the theoretical ethanol yield was observed in 36 h of fermentation.

Advances in industrial biotechnology offer potential opportunities for economic utilization of agro-industrial residues such as coffee pulp and coffee husk. Coffee pulp or husk is a fibrous mucilagenous material (sub-product) obtained during the processing of coffee cherries by wet or dry process, respectively. Coffee pulp/husk contains some amount of caffeine and tannins, which makes it toxic in nature, resulting the disposal problem. However, it is rich in organic nature, which makes it an ideal substrate for microbial processes for the production of value-added products. Several solutions and alternative uses of the coffee pulp and husk have been attempted. These include as fertilizers, livestock feed, compost, etc. However, these applications utilize only a fraction of available quantity and are not technically very efficient. Attempts have been made to detoxify it for improved application as feed, and to produce several products such as enzymes, organic acids, flavour and aroma compounds, and mushrooms, etc. from coffee pulp/husk. Solid state fermentation has been mostly employed for bioconversion processes. Factorial design experiments offer useful information for the process optimization. This paper reviews the developments on processes and products developed for the value-addition of coffee pulp/husk through the biotechnological means.

An effective method for the valorisation of the main by-product of biodiesel production, i.e. glycerol is investigated in this work. It involves the biological conversion of glycerol to succinic acid, a top added-value material, which can be used as a building block for the production of various commodity and specialty chemicals. Our aim is to give new insights into this bioprocess, which has so far received little attention and is open for further investigation, through a combination of experimental and computational studies. The microorganism employed here was Actinobacillus succinogenes in batch bioreactors where glycerol was used as the sole carbon source. The highest obtained product yield, final succinate concentration and productivity were found to be equal to 1.23. g-succinate/g-glycerol, 29.3. g-succinate/L and 0.27. g-succinate/L/h, respectively. Furthermore, an unstructured model of the batch experiments was developed by considering both substrate and product inhibition. Kinetic parameters of the model were estimated by minimising the difference between experimental and predicted values. The corresponding optimisation problem was solved by using a combination of stochastic and deterministic methodologies, with the goal to probabilistically compute global minima and the resulting parameter values. The model developed can be utilised to successfully predict the concentration profiles of the five most important state variables (biomass, glycerol, succinic acid, formic acid, and acetic acid) with different initial glycerol concentrations. Scaled-up experiments in larger-scale bioreactors were used for further validation purposes. Our model can be further used to compute optimal operating/parametric conditions, which maximise yield, productivity and/or the final succinic acid concentration. ?? 2011 Elsevier B.V.

In the present work, the potential of three white-rot fungi (WRF) ( Trametes versicolor , Ganoderma lucidum and Irpex lacteus ) to decolorize the commercial tannery dye – Black Dycem – was investigated. The decolorization ability of the three strains was studied in primary and secondary screenings. The results indicated that T. versicolor displayed the greatest decolorization ability, both in terms of extent and rapidity. To assess the potential of T. versicolor , decolorization tests were performed in single and repeated batches in an air-pulsed bioreactor with biomass reuse. Although low enzyme activity was detected during the repeated batches, the decolorization capability of the fungus did not decrease, and T. versicolor was able to remove 86–89% of the dye. Further experiments were conducted in order to elucidate the enzymatic activities involved in the dye biodegradation process. The results proved that the biodegradation mechanism plays a noticeable role in the decolorization process of the dye, in addition to adsorption phenomenon occurring on the fungal surface. Moreover, it was shown that laccase is involved in the decolorization process, although a mediator is required. Killed fungus presented an appreciable color removal even in repeated batches, suggesting that dead cells are an effective biosorbent.

A xylanase purified from Streptomyces rameus L2001 and the biobleaching effect on wheat straw pulp was investigated. The extracellular xylanase was purified 13.3-fold by precipitation with 40–60% (NH4)2SO4, DEAE-52 and CM Sepharose Fast Flow ion exchange chromatography. It appeared as a monomeric protein on SDS-PAGE gel and had a molecular mass of approx. 21.1 kDa, with a specific activity of 3236.6 U/mg. The purified xylanase had an optimum pH of 5.3 and was stable over pH 4.3–6.7. The stable optimal temperature of the enzyme was 70 °C. The xylanase was activated by Co2+ by up to 329% of baseline activity. The xylanase was highly specific towards xylan, but did not exhibit other enzyme activity. Apparent Km values of the xylanase for birchwood and beechwood were 5.8 and 5.3 mg mL−1, respectively. The potential application of the xylanase was further evaluated in wheat straw pulp. The amount of reducing sugars released by the xylanase from wheat straw pulp was significantly greater with increasing time. Enzymatic treatment at a charge of 20 U/g dry pulp for 1 h before hypochlorite (3.8%) treatment revealed an increase in brightness index by 2.8% and increase in residual chlorine by 14.5%.

We tested the nitrogen removal ability of a dual bag system. The dual bag was constructed with an outer non-woven fabric bag and an inner non-porous polyethylene film bag. Nitrosomonas europaea and Paracoccus pantotrophus were immobilized on the outer bag and 23 mL of 99.5% ethanol was packed into the inner hermetic bag. The dual bag removes ammonia as follows: ammonia in the solution is oxidized to nitrite, and the produced nitrite is reduced to nitrogen gas by cooperation of the N. europaea and P. pantotrophus on the outer bag. Ethanol as an electron donor for denitrification is supplied to the P. pantotrophus from the inner bag. Ammonia solution (20 mg N L−1) flowed into a reactor tank (200 mL volume) with three dual bags was continuously treated for a hydraulic retention time of 2.6 h at 25 °C. Total nitrogen in the outflow of the reactor was kept below 4.0 mg N L−1 for more than 90 days without accumulating organic carbons. The dual bags removed 80.0% of the nitrogen from the solution without additional operations. The inner bag containing 23 mL of ethanol probably releases ethanol for approximately 1000 days without refilling since the inner bag released only 0.022 mL ethanol per day. The dual bag system would effectively simplify the nitrogen removal system since it is easily installed in vacant spaces of various waterways and tanks.

The licensed UK anthrax vaccine is produced by static cultures of Bacillus anthracis Sterne 34F2 in glass Thompson bottles, each batch consisting of multiple bottles grown for 24–28 h. In this work, a novel miniature bioreactor was used as a scale-down tool to investigate the possible transfer of anthrax vaccine production from static culture to stirred tank operation and to explore the effects of this change in culture conditions on process performance. It is shown that the change to stirred culture conditions is possible and that the concentration of the two main vaccine components, Protective Antigen (PA) and Lethal Factor (LF), are reached in less than half the time compared to standard Thompson bottle methods. Furthermore, because higher cell densities were attained in the miniature bioreactor, a 74% increase in antigen concentration was achieved. More detailed analysis of the stirred bioreactor results operated with and without aeration showed antigen degradation in the presence of aeration. Overall this work demonstrates the usefulness of miniaturisation techniques to perform process characterisation studies safely and without significant capital investment for large-scale containment.

An open tank photobioreactor containing transparent rectangular chambers (TRCs) was developed to improve the photosynthetic efficiency of microalgal cultivation. The TRCs, made of transparent acrylic, conducted light deep into the photobioreactor, especially at high cell concentrations. The average irradiance, Iav, was calculated by Lambert–Beer's law, and was used to determine the light conditions in the cultivation system. The photobioreactor provided large areas of illumination that improved the effective utilization of light energy for microalgae growth and created a good artificial environment for a high rate of cell growth, even at low Iav. The biomass concentration of Chlorella sp. reached 3.745 g L−1 on the 13th day, with biomass productivity of 0.340 g L−1 d−1. The total biomass obtained was 56% more than that of similar culture systems without TRCs.

Cineolic essential oils are used in medicinal, perfumery and flavour preparations. 1,8-Cineole, being an ecofriendly compound, has the potential to replace the ozone depleting industrial solvents. Optimized process parameters for hydrodistillation and production of essential oil enriched with 1,8-cineole from Eucalyptus cinerea grown in the mid-hills of western Himalaya, were reported. The effect of drying of the foliage prior to distillation with respect to oil composition and content was studied. The first order kinetic and Langmuir adsorption models were evaluated to simulate hydrodistillation of E. cinerea oil. The Langmuir model parameters that simulate the hydrodistillation process were determined. GCMS analysis revealed that the oil produced from fresh foliage contained higher 1,8-cineole content (84.4%) than the dried foliage (77.6%). The other major constituents were limonene and α-terpineol.

An indigenous phenol-degrading bacterial isolate Cupriavidus taiwanensis R186 was used to degrade phenol from an aqueous solution under fed-batch operation. An exponential feeding strategy combined with dissolved oxygen control was applied based on kinetic characteristics of cell growth and phenol degradation to meet sufficient metabolic needs for cellular growth and achieve the best phenol removal efficiency. Without the stress of phenol inhibition, the optimal set point of specific growth rate of exponential feeding for fed-batch phenol degradation was found to be 0.50–0.55μmax (μmax denotes the maximum specific growth rate from Monod model). Meanwhile, the sufficient set point of dissolved oxygen for maximal phenol degradation efficiency was approximately at 10–55% air saturation. With the optimal operation conditions, the best phenol degradation rate was 0.213 g phenol h−1, while a shortest treatment time of 15 h was achieved for complete degradation of 11.35 mM (ca. 3.20 g) of phenol.

Biosurfactants have gained attention because they exhibit some advantages such as biodegradability, low toxicity, ecological acceptability and ability to be produced from renewable and cheaper substrates. They are widely used for environmental applications for bioremediation and also in biomedical field. However, the high cost of production is the limiting factor for widespread industrial applications. Thus, optimization of the growth medium for biosurfactant-lichenysin production by Bacillus licheniformis R2 was carried out using response-surface methodology. A preliminary screening phase based on a two-level fractional factorial design led to the identification of NH4NO3, glucose, Na2HPO4 and MnSO4·4H2O concentrations as the most significant variables affecting the fermentation process. The 24 full-factorial central composite design was then applied to further optimize the biosurfactant production. The optimal levels of the aforementioned variables were (g/l): NH4NO3, 1.0; glucose, 34.0; KH2PO4, 6.0; Na2HPO4, 2.7; MgSO4·7H2O, 0.1; CaCl2, 1.2 × 10−3; FeSO4·7H2O, 1.65 × 10−3; MnSO4·4H2O, 1.5 × 10−3 and Na–EDTA, 2.2 × 10−3. With the optimization procedure, the relative lichenysin yield expressed as the critical micelle dilution (CMD) was fourfold higher than that obtained in the non-optimized reference medium.