Influence of Exogenous CO2 on Biomass and Lipid Accumulation of Microalgae Auxenochlorella protothecoides Cultivated in Concentrated Municipal Wastewater

The effects of exogenous CO₂ on the growth and lipid accumulation of a local screened facultative heterotrophic microalgae strain Auxenochlorella protothecoides (UMN280) as well as nutrient removal from concentrated municipal wastewater stream (centrate) were examined in this study. A 12-day batch experiment was conducted with CO₂ aeration at three levels, namely, 0%, 1%, and 5% (v/v) CO₂ mixed with air, under light intensity of 60???mol/(m² @@s). A two-stage growth pattern was observed. The first stage (first?Cfifth day) was dominated by heterotrophic growth in which organic carbon was the main carbon source. The second stage (6th?C12th day) was dominated by autotrophic growth in which exogenous CO₂ had a positive effect on algal biomass accumulation. The addition of 5% CO₂ was better than that of 1% CO₂ on the biomass and lipid production. The uptakes of nutrients were similar between injection and no injection of CO₂, except on phosphorus removal which was affected by the acidification of CO₂.     

Optimisation of Batch Culture Conditions for Cell-Envelope-Associated Proteinase Production from Lactobacillus delbrueckii subsp. lactis ATCC? 7830?

Using a combination of conventional sequential techniques, the batch growth conditions for the production of cell-envelope-associated proteinases have for the first time been studied and optimised in Lactobacillus delbrueckii subsp. lactis 313 (ATCC 7830; LDL 313). Concentrations of inoculum (0.1?<?X?<?10?% vol/vol), agitation speed (0?<?S?<?200?rpm), varying incubation temperature (30?<?T?<?50?°C), starting pH (4.5?<?pH?<?7) and carbon/nitrogen ratio of production medium (0.2?<?r?<?5) had an individual effect on proteinase yield (p?<?0.01). Optimal conditions for proteinase production included an initial pH of 6.0, 45?°C incubation temperature, 2?% (v/v) inoculum size of OD₅₆₀?=?1, 150?rpm agitation speed, and growth medium carbon/nitrogen ratio of 1.0. Maximum proteinase activity obtained for whole cells was 0.99 U/ml after 8?h of incubation. The variables studied are very relevant due to their significance in improving the productivity of proteinase synthesis from LDL 313, under process and, likely, economic optimum conditions.     

Bioethanol Production Involving Recombinant C. thermocellum Hydrolytic Hemicellulase and Fermentative Microbes

The enhancement of the biomass productivity of Escherichia coli cells harbouring the truncated 903?bp gene designated as glycoside hydrolase family 43 (GH43) from Clostridium thermocellum showing hemicellulase activity along with its further use in simultaneous saccharification and fermentation (SSF) process is described. (Phosphoric acid) H₃PO₄?Cacetone treatment and ammonia fibre expansion (AFEX) were the pretreatment strategies employed on the leafy biomass of mango, poplar, neem and asoka among various substrates owing to their high hemicellulose content. GH43 showed optimal activity at a temperature of 50?°C, pH?5.4 with stability over a pH range of 5.0?C6.2. A 4-fold escalation in growth of the recombinant E. coli cells was observed when grown using repeated batch strategy in LB medium supplemented with glucose as co-substrate. Candida shehatae utilizing pentose sugars was employed for bioethanol production. AFEX pretreatment proved to be better over acid?Cacetone technique. The maximum ethanol concentration (1.44?g/L) was achieved for AFEX pretreated mango (1%, w/v) followed by poplar with an ethanol titre (1.32?g/L) in shake flask experiments. A 1.5-fold increase in ethanol titre (2.11?g/L) was achieved with mango (1%, w/v) in a SSF process using a table top 2-L bioreactor with 1?L working volume.     

Optimal glucose and inoculum concentrations for production of bioactive molecules by Paenibacillus polymyxa RNC-D

The production of antimicrobial metabolites by Paenibacillus polymyxa RNC-D was assessed. Two process variables, glucose and inoculum concentrations, were evaluated at different levels (5?C40 g L^?1, and at ?? _r = 2.5?C5.0 %, respectively), and their effects on biomass formation, minimal inhibitory concentration (MIC) against Escherichia coli, and surface tension reduction (STR) were studied. When the fermentation process was carried out under non-optimised conditions, the biomass, MIC, and STR achieved the following values: 0.6 g L^?1, 1 g L^?1, and 18.4 mN m^?1, respectively. The optimum glucose (16 g L^?1) and inoculum volume ratio (?? _r = 5.0 %) were defined in order to maximise the biomass formation, with a low value of MIC and high STR of extract. The experiments carried out under optimal conditions showed the following values for the dependent variables: biomass concentration 2.05 g L^?1, MIC 31.2 ??g mL^?1, and STR 10.7 mN m^?1, which represented improvement of 241.7 %, 96.9 %, and 41.9 % for the responses of biomass, MIC, and STR, respectively. This is the first recorded study on the optimisation of culture conditions for the production of antimicrobial metabolites of P. polymyxa RNC-D, and constitutes an important step in the development of strategies to modulate the production of antimicrobial molecules by this microorganism at elevated levels.     

An Indigenous Hyperproductive Species of Aureobasidium pullulans RYLF-10: Influence of Fermentation Conditions on Exopolysaccharide (EPS) Production

In recent years, a significant interest has been generated in discovering and developing exopolysaccharides (EPS) produced by microorganisms, especially fungi due to their multifaceted industrial and pharmacological applications. A number of filamentous and cellular fungi have been explored for this; however, according to the existing literature, the work on exopolysaccharide production by indigenous culture on this aspect is still very less and requires a serious attention. The present work is an attempt in this regard and aims to optimize the submerged culture conditions to produce the exopolysaccharides from an indigenous yeast Aureobasidium pullulans RYLF-10 with respect to several operating parameters in shake flask fermentation. The yeast A. pullulans RYLF-10 was identified by 18s RNA sequencing and detailed study on its nutritional requirements, and environmental conditions for submerged culture have been optimized. The optimal temperature and pH for both the vegetative growth and EPS production were found to be 28?±?1 °C and 5.0, respectively, while the agitation speed and inoculum size were reported to be 150 rpm and 1 % (v/v), respectively. Sucrose (50 g/l) and yeast extract (1 g/l) were found to be the most suitable carbon and nitrogen sources which worked best in the ratio of 60:1 and resulted in the maximum EPS yield. Similarly, the other variables like growth regulator (riboflavin) and minerals (NaCl?+?K₂HPO₄?+?MgSO₄) altogether resulted in a noteworthy EPS yield of 45.24 g/l which is the maximum yield from this indigenous isolate of A. pullulans RYLF-10.     

Potential of using a single fermenter for biomass build-up,starch hydrolysis,and ethanol production

Data on conversion of starch on biomass and ethanol bySchwanniomyces castellii in an aerobic-anaerobic solid state fermentation is reported.Schwanniomyces castellii grew exponentially in the aerobic phase (12 h) and simultaneously hydrolyzed nearly half (55%) of the starch initially present. The accumulation of glucose increased up to 12 h, whereas maltose was nearly absent beyond 7 h. Shift of metabolism from oxidative to fermentative pattern was observed about 10 h as a result of the build-up of CO₂ level and faster utilization of O₂. The ethanol production in the anaerobic phase reached the level of 89.3 mg ethanol/g initial dry matter by the end of 30 h. A total of 92.9% of the starch is utilized during the fermentation. The overall ethanol conversion yields are 57.8% of the theoretical value, whereas in the anaerobic phase it was found to be 94.4%. The cell shape, its morphology, and the type of attachment to the solid support were found to be similar in aerobic and anaerobic phases of fermentation. Data given in this work indicate the feasibility of using one single fermenter for aerobic growth to generate inoculum as well as to simultaneously hydrolyze the starch and subsequent anaerobic fermentation to produce ethanol.     

Enhanced Fumaric Acid Production from Brewery Wastewater and Insight into the Morphology of Rhizopus oryzae 1526

The present work explores brewery wastewater as a novel substrate for fumaric acid production employing the filamentous fungal strain Rhizopus oryzae 1526 through submerged fermentation. The effects of different parameters such as substrate total solid concentrations, fermentation pH, incubation temperature, flask shaking speed, and inoculum size on the fungal morphologies were investigated. Different morphological forms (mycelium clumps, suspended mycelium, and solid/hairy pellets) of R. oryzae 1526 were obtained at different applied fermentation pH, incubation temperature, flask shaking speed, and inoculum size. Among all the obtained morphologies, pellet morphology was found to be the most favorable for enhanced production of fumaric acid for different studied parameters. Scanning electron microscopic investigation was done to reveal the detailed morphologies of the pellets formed under all optimized conditions. With all the optimized growth conditions (pH 6, 25 °C, 200 rpm, 5 % (v/v) inoculum size, 25 g/L total solid concentration, and pellet diameter of 0.465?±?0.04 mm), the highest concentration of fumaric acid achieved was 31.3?±?2.77 g/L. The results demonstrated that brewery wastewater could be used as a good substrate for the fungal strain R. oryzae 1526 in submerged fermentation for the production of fumaric acid.     

Phase behaviour of tri-n-butylmethylammonium chloride hydrates in the presence of carbon dioxide

The phase behaviour of the system water?Ctri-n-butylmethylammonium chloride (TBMAC)?CCO₂ was investigated by pressure-controlled differential scanning calorimetry in the range 0?C10?mol% TBMAC in water and at CO₂ pressures ranging from 0 to 1.5?MPa. In the absence of CO₂, an incongruent melting hydrate, which estimated composition corresponds to TBMAC·30H₂O, crystallizes at temperatures below ?13.6?°C and forms with ice a peritectic phase at approximately 3.9?mol% TBMAC. In the presence of CO₂ at pressures as low as 0.5?MPa, curves evidenced the presence of an additional phase exhibiting congruent melting at temperatures that are strongly pressure dependent and significantly higher than those of hydrates obtained without CO₂. This new phase, whose enthalpy of dissociation and CO₂ content increase slightly with CO₂ pressure, was identified as a mixed semi-clathrate hydrate of TBMAC and CO₂ of general formula: (TBMAC?+?xCO₂)·30H₂O.     

High-resolution UV photoelectron spectrum of CO2

The highly-resolved HeI photoelectron spectrum of CO₂ is presented and its vibrational structure studied in detail. In the X? ²Π_g ionic state the v₃ antisymmetric mode is found to be excited in double quanta (v_1-v_2-v₃ = 0. 0. 2) with energy hv₃ = 181 meV. In the C? ²Σ_g⁺ state a single quantum of the same mode is found to be excited (hv₃ = 189 meV) in combination with a v₁ excitation. Vibronic interaction with vibrational levels in the B? ²Σ_u⁺ state of the ion is suggested to promote this (1, 0, 1) excitation. It is established that inelastic scattering processes contribute to the vibrational structure in the C? ²Σ_g⁺ band. The spin-orbit splitting in the X? ²Π_g is determined to be 19±1 meV and 10±2 eV in the ā²Π_u state. Vibronic structure is resolved in the X? ²Π_g band where the Renner-Teller coupling constant is determined to be ? = 0.21±0.02 and the vibrational energy of the v₂ mode as 60±7 meV. In the ā²Π_u state the v₂ energy is found to be hv₂ = 60 meV from the observed hot-band structure.     

Application of quantitative IR spectral analysis of bacterial cells to acetone-butanol-ethanol fermentation monitoring

Clostridium acetobutylicum ATCC 824 was grown under three different acetone-butanol-ethanol (ABE) fermentation conditions: (1) strictly anaerobic conditions with vegetative inoculum; (2) semi-anaerobic conditions with vegetative inoculum; and (3) strictly anaerobic conditions with spore inoculum. Semi-anaerobic fermentation with vegetative inoculum and strictly anaerobic fermentation with spore inoculum produced solvents at high level. Strictly anaerobic fermentation with vegetative inoculum showed an “acid crash”, i.e. produced mainly acids and did not switch to predominant solvent production. The content of carbohydrates, nucleic acids, proteins and lipids in Clostridium cells during the fermentation were evaluated from the mid-IR spectra. The content of nucleic acids decreased with process time, and the lipid content increased, corresponding to ceasing growth and formation of the toxic fermentation products. It was shown that the physiological states of either solvent production or acid crash are reflected in the microbial biomass composition, which can be assessed by IR spectroscopy.     

Controlled Continuous Bio-Hydrogen Production Using Different Biogas Release Strategies

Dark fermentation for bio-hydrogen (bio-H₂) production is an easily operated and environmentally friendly technology. However, low bio-H₂ production yield has been reported as its main drawback. Two strategies have been followed in the past to improve this fact: genetic modifications and adjusting the reaction conditions. In this paper, the second one is followed to regulate the bio-H₂ release from the reactor. This operating condition alters the metabolic pathways and increased the bio-H₂ production twice. Gas release was forced in the continuous culture to study the equilibrium in the mass transfer between the gaseous and liquid phases. This equilibrium depends on the H₂, CO₂, and volatile fatty acids production. The effect of reducing the bio-H₂ partial pressure (bio-H₂?pp) to enhance bio-H₂ production was evaluated in a 30 L continuous stirred tank reactor. Three bio-H₂ release strategies were followed: uncontrolled, intermittent, and constant. In the so called uncontrolled fermentation, without bio-H₂?pp control, a bio-H₂ molar yield of 1.2 mol/mol glucose was obtained. A sustained low bio-H₂?pp of 0.06 atm increased the bio-H₂ production rate from 16.1 to 108 mL/L/h with a stable bio-H₂ percentage of 55 % (v/v) and a molar yield of 1.9 mol/mol glucose. Biogas release enhanced bio-H₂ production because lower bio-H₂ pp, CO₂ concentration, and reduced volatile fatty acids accumulation prevented the associated inhibitions and bio-H₂ consumption.     

Effectiveness of Sal Deoiled Seed Cake as an Inducer for Protease Production from Aeromonas sp. S1 for its Application in Kitchen Wastewater Treatment

The present study is an attempt to demonstrate the feasibility of sal (Shorea robusta) deoiled cake—a forest-based industrial by-product—as a cheaper media supplement for augmented protease production from Aeromonas sp. S1 and application of protease in the treatment of kitchen wastewater. Under optimized conditions, protease production could successfully be enhanced to 5.13-fold (527.5 U mL^?1) on using sal deoiled seed cake extract (SDOCE), as medium additive, compared to an initial production of 102.7 U mL^?1 in its absence. The culture parameters for optimum production of protease were determined to be incubation time (48 h), pH (7.0), SDOCE concentration (3 % (v/v)), inoculum size (0.3–0.6 % (v/v)), and agitation rate (100 rpm). The enzyme was found to have an optimum pH and temperature of 8.0 and 60 °C, respectively. The protease preparation was tested for treatment of organic-laden kitchen wastewater. After 96 h of wastewater treatment under static condition, enzyme preparation was able to reduce 74 % biological oxygen demand, 37 % total suspended solids, and 41 % oil and grease. The higher and improved level of protease obtained using sal deoiled seed cake-based media hence offers a new approach for value addition to this underutilized biomass through industrial enzyme production. The protease produced using this biomass could also be used as pretreatment tool for remediation of organic-rich food wastewater.     

Vibration excitation of no in its collisional quenching of O2 (1▵g)

Infrared emission of NO from levels up to v = 4 is observed in its gas phase quenching of O₂(¹ ?_g). The predominance of population of the highest accessible level of NO (v = 4) is due to matching of energies.     

Vibrational energy transfer from C2H4 to CO2 studied at low temperatures in a jet by infrared double resonance

In a mixed CO₂-C₂H₄ jet the populations of rotational levels in the ground andv ₂ (667 cm^?1) vibrational state of CO₂ are probed by color center laser absorption. The rotational distributions are well described by a rotational temperature. On the timescale of the expansion thev ₂ state does only relax through resonant deexcitation by CO₂ clusters. A 10% fraction of C₂H₄ molecules is excited into thev ₇ (949 cm^?1) level by CW CO₂ laser absorption, subsequently releasing energy into the expansion due to relaxation to lower C₂H₄ vibrational states and to thev ₂ mode of CO₂. Observed are the induced rise of rotational temperature and the increase ofv ₂ level population. By probing at several distances from the nozzle the temperature range from 30–155 K is covered. The vibrational transfer of the excited C₂H₄ to thev ₂ level of CO₂ has a near quadratic inverse temperature dependence, increasing by a factor of 40 when the temperature is lowered from 155 K to 30 K.     

Effect of CO2 Concentration on Growth and Biochemical Composition of Newly Isolated Indigenous Microalga Scenedesmus bajacalifornicus BBKLP-07

Photosynthetic mitigation of CO₂ through microalgae is gaining great importance due to its higher photosynthetic ability compared to plants, and the biomass can be commercially exploited for various applications. CO₂ fixation capability of the newly isolated freshwater microalgae Scenedesmus bajacalifornicus BBKLP-07 was investigated using a 1-l photobioreactor. The cultivation was carried at varying concentration of CO₂ ranging from 5 to 25%, and the temperature and light intensities were kept constant. A maximum CO₂ fixation rate was observed at 15% CO₂ concentration. Characteristic growth parameters such as biomass productivity, specific growth rate, and maximum biomass yield, and biochemical parameters such as carbohydrate, protein, lipid, chlorophyll, and carotenoid were determined and discussed. It was observed that the effect of CO₂ concentration on growth and biochemical composition was quite significant. The maximum biomass productivity was 0.061 ± 0.0007 g/l/day, and the rate of CO₂ fixation was 0.12 ± 0.002 g/l/day at 15% CO₂ concentration. The carbohydrate and lipid content were maximum at 25% CO₂ with 26.19 and 25.81% dry cell weight whereas protein, chlorophyll, and carotenoid contents were 32.89% dry cell weight, 25.07 μg/ml and 6.15 μg/ml respectively at 15% CO₂ concentration.

     

Stimulation of hydrogen production in algal cells grown under high CO2 concentration and low temperature

When cells ofChlamydomonas sp. MGA 161, a marine green alga, were cultivated at a high CO₂ concentration (15% CO₂) and low temperature (15°C), the growth lag time was much longer, but the starch accumulated was two times higher than under the basal conditions (5% CO₂ 30°C). When the cells grown in the high-CO₂/low-temperature conditions were incubated under dark anaerobic conditions, the degradation of starch and production of hydrogen and ethanol were remarkably higher than those grown under the basal conditions. The lag time of cell growth was shortened, whereas the high capacity of starch accumulation and hydrogen production was maintained, by cultivating the cells alternately every 12 h under the basal and high-CO₂/low-temperature conditions. Using this dual system, in which the cultivation was alternated between the two conditions, the total productivity was significantly improved.     

Simultaneous HPLC Determination of Four Key Metabolites in the Metabolic Pathway for Production of 1,3-Propanediol from Glycerol

A high-performance liquid chromatographic (HPLC) method with refractive-index detection has been developed for simultaneous analysis of glycerol, dihydroxyacetone (DHA), 3-hydroxypropionaldehyde (3-HPA), and 1,3-propanediol (1,3-PD), four key substances in the metabolic pathway for production of 1,3-PD from glycerol by microorganism fermentation. The compounds were separated on a 300 mm × 7.8 mm ion-exclusion column with a 65:35 (v/v) mixture of deionized water and acetonitrile, containing 0.0005 M H₂SO₄, as mobile phase. The flow rate was 0.5 mL min^?1. Under these conditions the retention times of 3-HPA, DHA, glycerol, and 1,3-PD were 6.87, 14.63, 16.37, and 18.50 min, respectively. Relative standard deviations and average recoveries were between 0.42 and 0.63% and between 96.7 and 103.1%, respectively; detection limits were between 0.017 and 0.038 g L^?1. The method enabled separation of these compounds.     

Raman studies of pressure tuning of the fermi resonance in solid CO2

Raman studies on the v₁, 2v₂ Fermi doublet in solid CO₂ up to 100 kbar at ambient temperature show the upper peak to increase and the lower peak to decrease both in intensity and frequency. It is concluded that the bare v₁ is above the bare 2v₂ at all pressures in solid CO₂.     

Alcoholic Fermentation with Flocculant Saccharomyces cerevisiae in Fed-Batch Process

Studies have been conducted on selecting yeast strains for use in fermentation for ethanol production to improve the performance of industrial plants and decrease production costs. In this paper, we study alcoholic fermentation in a fed-batch process using a Saccharomyces cerevisiae yeast strain with flocculant characteristics. Central composite design (CCD) was used to determine the optimal combination of the variables involved, with the sucrose concentration of 170 g/L, a cellular concentration in the inoculum of 40 % (v/v), and a filling time of 6 h, which resulted in a 92.20 % yield relative to the theoretical maximum yield, a productivity of 6.01 g/L h and a residual sucrose concentration of 44.33 g/L. With some changes in the process such as recirculation of medium during the fermentation process and increase in cellular concentration in the inoculum after use of the CCD was possible to reduce the residual sucrose concentration to 2.8 g/L in 9 h of fermentation and increase yield and productivity for 92.75 % and 9.26 g/L h, respectively. A model was developed to describe the inhibition of alcoholic fermentation kinetics by the substrate and the product. The maximum specific growth rate was 0.103 h^?1, with K _I and K _s values of 109.86 and 30.24 g/L, respectively. The experimental results from the fed-batch reactor show a good fit with the proposed model, resulting in a maximum growth rate of 0.080 h^?1.