Biological treatment of refinery spent caustics under halo-alkaline conditions

The present research demonstrates the biological treatment of refinery sulfidic spent caustics in a continuously fed system under halo-alkaline conditions (i.e. pH 9.5; Na⁺ = 0.8 M). Experiments were performed in identical gas-lift bioreactors operated under aerobic conditions (80-90% saturation) at 35 °C. Sulfide loading rates up to 27 mmol L⁻¹ day⁻¹ were successfully applied at a HRT of 3.5 days. Sulfide was completely converted into sulfate by the haloalkaliphilic sulfide-oxidizing bacteria belonging to the genus Thioalkalivibrio. Influent benzene concentrations ranged from 100 to 600 μM. At steady state, benzene was removed by 93% due to high stripping efficiencies and biodegradation. Microbial community analysis revealed the presence of haloalkaliphilic heterotrophic bacteria belonging to the genera Marinobacter, Halomonas and Idiomarina which might have been involved in the observed benzene removal. The work shows the potential of halo-alkaliphilic bacteria in mitigating environmental problems caused by alkaline waste.     

Accumulation of lead by free and immobilized cyanobacteria with special reference to accumulation factor and recovery

Lead accumulation by free and immobilized cyanobacteria, Lyngbya majuscula and Spirulina subsalsa was studied. Exponentially growing biomass was exposed to 1-20 mg L⁻¹ of Pb(II) solution at pH 6, 7 and 8 for time periods ranging from 10 min to 48 h. L. majuscula accumulated 10 times more Pb (13.5 mg g⁻¹) than S. subsalsa (1.32 mg g⁻¹) at pH 6 within 3 h of exposure to 20 mg L⁻¹ Pb(II) solution and 76% of the Pb could be recovered using 0.1 M EDTA. This chelator (2 μM) did not influence Pb accumulation whereas 100 μM citrate increased that of S. subsalsa 6- to 8-fold. L. majuscula filaments enmeshed in a glass wool packed in a column removed 95.8% of the Pb from a 5 mg L⁻¹ Pb solution compared to free and dead biomass which removed 64 and 33.6% Pb respectively. A 92.5% recovery of accumulated Pb from the immobilized biomass suggests that repeated absorption-desorption is possible.     

Influence of ammonium sulphate feeding time on fed-batch Arthrospira (Spirulina) platensis cultivation and biomass composition with and without pH control

Previous work demonstrated that a mixture of NH₄Cl and KNO₃ as nitrogen source was beneficial to fed-batch Arthrospira (Spirulina) platensis cultivation, in terms of either lower costs or higher cell concentration. On the basis of those results, this study focused on the use of a cheaper nitrogen source mixture, namely (NH₄)₂SO₄ plus NaNO₃, varying the ammonium feeding time (T = 7-15 days), either controlling the pH by CO₂ addition or not. A. platensis was cultivated in mini-tanks at 30 °C, 156 μmol photons m⁻² s⁻¹, and starting cell concentration of 400 mg L⁻¹, on a modified Schlösser medium. T = 13 days under pH control were selected as optimum conditions, ensuring the best results in terms of biomass production (maximum cell concentration of 2911 mg L⁻¹, cell productivity of 179 mg L⁻¹ d⁻¹ and specific growth rate of 0.77 d⁻¹) and satisfactory protein and lipid contents (around 30% each).     

Laboratory experiments on the effects of variable suspended sediment concentrations on the ecophysiology of the porcelain crab Petrolisthes elongatus (Milne Edwards, 1837)

The porcelain crab Petrolisthes elongatus is a particulate suspension feeding species common to coastal areas of New Zealand (NZ). Consistent with the responses of other suspension feeding species, it is likely to be negatively influenced by elevated suspended sediment concentrations. Laboratory experiments were conducted to quantify the effect of temperature (12 °C, 15 °C and 18 °C) and suspended sediment concentration (total particulate matter (TPM): low < 100 mg L^− 1; medium 100-1000 mg L^− 1; high > 1000 mg L^− 1) on the clearance rate (CR in L h^− 1), oxygen uptake rate (VO₂ in mL h⁻¹), net absorption efficiency (AE), and net energy budget (NEB in J h^− 1) of P. elongatus across a range of sizes. Variation in CR and AE was independent of temperature and of body size, but were significantly different (P < 0.05) at low and medium suspended sediment concentrations compared with high suspended sediment concentrations. CR responded in a non-linear manner to changes in TPM, increasing with TPM up to a maximum value at medium-low concentrations (approximately 250 mg L^− 1) and then decreasing thereafter. CR had almost completely shut down at TPM concentrations of > 1000 mg L^− 1 and at particulate organic matter (POM) concentrations of > 250 mg L^− 1. AE was zero at approximate TPM and POM values of 1200 mg L^− 1 and 300 mg L^− 1, respectively. VO₂ was positively correlated with body size and with temperature, but was independent of TPM. NEB values for P. elongatus were low (approx 110 J g^− 1 h^− 1) at low sediment concentrations, were high (approx 320 J g^− 1 h^− 1) at medium sediment concentrations, and were negative (approx − 114 J g^− 1 h^− 1) at high sediment concentrations. These findings indicate that P. elongatus is likely to be food-limited at sediment concentrations of < 100 mg L^− 1, and severely negatively affected at sediment concentrations of > 1000 mg L^− 1, at least for the duration of such events which may persist for 2-3 days in coastal environments where this crab occurs.     

Vertical tubular photobioreactor for semicontinuous culture of Cyanobium sp

We evaluated the kinetic culture characteristics of the microalgae Cyanobium sp. grown in vertical tubular photobioreactor in semicontinuous mode. Cultivation was carried out in vertical tubular photobioreactor for 2 L, in 57 d, at 30 °C, 3200 Lux, and 12 h light/dark photoperiod. The maximum specific growth rate was found as 0.127 d⁻¹, when the culture had blend concentration of 1.0 g L⁻¹, renewal rate of 50%, and sodium bicarbonate concentration of 1.0 g L⁻¹. The maximum values of productivity (0.071 g L⁻¹ d⁻¹) and number of cycles (10) were observed in blend concentration of 1.0 g L⁻¹, renewal rate of 30%, and bicarbonate concentration of 1.0 g L⁻¹. The results showed the potential of semicontinuous cultivation of Cyanobium sp. in closed tubular bioreactor, combining factors such as blend concentration, renewal rate, and sodium bicarbonate concentration.     

Ecology of aquatic Ranunculus communities under the Mediterranean climate

The Iberian Peninsula encompasses more than 80% of the species richness of European aquatic ranunculi. The floristic diversity of the phytocoenosis characterised by aquatic Ranunculus and the main physical–chemical factors of the water were studied in 43 localities of the central Iberian Peninsula. Four aquatic Ranunculus communities are found in most of the aquatic environments. These are species-poor and have an uneven distribution: three species of Batrachium are heterophyllous and their communities are distributed in different aquatic ecosystems on silicated substrates; one species is homophyllous and its community occurs in various aquatic ecosystems with carbonated waters. In the Mediterranean climate, Ranunculus species are present in different habitats, as shown by the results of all the statistical analyses. Ranunculus trichophyllus communities occur in base-rich waters with a high buffering capacity (2273.44 ± 794.57 mg CaCO₃ L⁻¹) and a high concentration of cations (Ca²⁺, 121 ± 33.12 mg L⁻¹; Mg²⁺, 71.64 ± 82.77 mg L⁻¹), nitrates (2.89 ± 4.80 mg L⁻¹), ammonium (2.19 ± 1.36 mg L⁻¹) and sulphates (216.25 ± 218.54 mg L⁻¹). Ranunculus penicillatus communities are found in flowing waters with a high concentration of phosphates (0.48 ± 0.6 mg L⁻¹) and intermediate buffering capacity (683.66 ± 446.76 mg CaCO₃ L⁻¹). Both Ranunculus pseudofluitans and Ranunculus peltatus communities grow in waters with low buffering capacity (R. pseudofluitans, 385.91 ± 209.2 mg CaCO₃ L⁻¹; R. peltatus, 263.3 ± 180.36 mg CaCO₃ L⁻¹), and a low concentration of cations (R. pseudofluitans: Ca²⁺, 12.57 ± 9.42 mg L⁻¹; Mg²⁺, 3.42 ± 1.67 mg L⁻¹; R. peltatus: Ca²⁺, 15 ± 18.26 mg L⁻¹; Mg²⁺, 6.26 ± 8.89 mg L⁻¹) and nutrients (R. pseudofluitans: nitrates, 0.23 ± 0.2 mg L⁻¹; phosphates, 0.09 ± 0.1 mg L⁻¹; R. peltatus: nitrates, 0.19 ± 0.21 mg L⁻¹; phosphates, 0.09 ± 0.12 mg L⁻¹); the first in flowing waters, the latter in still waters.     

Bicarbonate use in three aquatic plants

Our study aimed to test the ability of aquatic plants to use bicarbonate when acclimated to three different bicarbonate concentrations. To this end, we performed experiments with the three species Ceratophyllum demersum, Egeria densa, Lagarosiphon major to determine photosynthetic rates under varying bicarbonate concentrations. We measured bicarbonate use efficiency, photosynthetic performance and respiration. For all species, our results revealed that photosynthetic rates were highest in replicates grown at low alkalinity. Thus, E. densa had approx. five times higher rates at low (264 ± 15 μmol O₂ g⁻¹ DW h⁻¹) than at high alkalinity (50 ± 27 μmol O₂ g⁻¹ DW h⁻¹), C. demersum had three times higher rates (336 ± 95 and 120 ± 31 μmol O₂ g⁻¹ DW h⁻¹), and L. major doubled its rates at low alkalinity (634 ± 114 and 322 ± 119 μmol O₂ g⁻¹ DW h⁻¹). Similar results were obtained for bicarbonate use efficiency by E. densa (136 ± 44 and 43 ± 10 μmol O₂ mequiv. L⁻¹ g⁻¹ DW h⁻¹) and L. major (244 ± 29 and 82 ± 24 μmol O₂ mequiv. L⁻¹ g⁻¹ DW h⁻¹). As to C. demersum, efficiency was high but unaffected by alkalinity, indicating high adaptation ability to varied alkalinities. A pH drift experiment supported these results. Overall, our results suggest that the three globally widespread worldwide species of our study adapt to low inorganic carbon availability by increasing their efficiency of bicarbonate use.     

In silico optimization and low structured kinetic model of poly[(R)-3-hydroxybutyrate] synthesis by Cupriavidus necator DSM 545 by fed-batch cultivation on glycerol

Glycerol was utilized by Cupriavidus necator DSM 545 for production of poly-3-hydroxybutyrate (PHB) in fed-batch fermentation. Maximal specific growth rates (0.12 and 0.3 h⁻¹) and maximal specific non-growth PHB production rate (0.16 g g⁻¹ h⁻¹) were determined from two experiments (inocula from exponential and stationary phase). Saturation constants for nitrogen (0.107 and 0.016 g L⁻¹), glycerol (0.05 g L⁻¹), non-growth related PHB synthesis (0.011 g L⁻¹) and nitrogen/PHB related inhibition constant (0.405 g L⁻¹), were estimated. Five relations for specific growth rate were tested using mathematical models. In silico performed optimization procedures (varied glycerol/nitrogen ratio and feeding) has resulted in a PHB content of 70.9%, shorter cultivation time (23 h) and better PHB yield (0.347 g g⁻¹). Initial concentration of biomass 16.8 g L⁻¹ and glycerol concentration in broth between 3 and 5 g L⁻¹ were decisive factors for increasing of productivity.     

Development of chemically defined media supporting high cell density growth of Ketogulonicigenium vulgare and Bacillus megaterium

The immediate precursor of L-ascorbic acid, or vitamin C, is 2-keto-l-gulonic acid (2-KLG). This is commonly produced commercially by Ketogulonicigenium vulgare and Bacillus megaterium, using corn steep liquor powder (CSLP) as an organic nitrogen source. In this study, the effects of the individual CSLP components (amino acids, vitamins, and metal elements) on 2-KLG production were evaluated, with the aim of developing a complete, chemically defined medium for 2-KLG production. Forty components of CSLP were analyzed, and key components were correlated to biomass, 2-KLG productivity, and consumption rate of L-sorbose. Glycine had the greatest effect, followed by serine, biotin, proline, nicotinic acid, and threonine. The combination of 0.28 g L⁻¹ serine, 0.36 g L⁻¹glycine, 0.18 g L⁻¹ threonine, 0.28 g L⁻¹proline, 0.19 g L⁻¹nicotinic acid, and 0.62 mg L⁻¹biotin in a chemically defined medium produced the highest maximum biomass concentration (4.2 × 10⁹ cfu mL⁻¹), 2-KLG concentration (58 g L⁻¹), and yield (0.76 g g⁻¹) after culturing for 28 h.     

Treatment of industrial wastewater with two-stage constructed wetlands planted with Typha latifolia and Phragmites australis

Industrial wastewater treatment comprises several processes to fulfill the discharge permits or to enable the reuse of wastewater. For tannery wastewater, constructed wetlands (CWs) may be an interesting treatment option. Two-stage series of horizontal subsurface flow CWs with Phragmites australis (UP series) and Typha latifolia (UT series) provided high removal of organics from tannery wastewater, up to 88% of biochemical oxygen demand (BOD₅) (from an inlet of 420 to 1000 mg L⁻¹) and 92% of chemical oxygen demand (COD) (from an inlet of 808 to 2449 mg L⁻¹), and of other contaminants, such as nitrogen, operating at hydraulic retention times of 2, 5 and 7 days. No significant (P < 0.05) differences in performance were found between both the series. Overall mass removals of up to 1294 kg COD ha⁻¹ d⁻¹ and 529 kg BOD₅ ha⁻¹ d⁻¹ were achieved for a loading ranging from 242 to 1925 kg COD ha⁻¹ d⁻¹ and from 126 to 900 kg BOD₅ ha⁻¹ d⁻¹. Plants were resilient to the conditions imposed, however P. australis exceeded T. latifolia in terms of propagation.     

Ethanol production from syngas by Clostridium strain P11 using corn steep liquor as a nutrient replacement to yeast extract

The feasibility of replacing yeast extract (YE) by corn steep liquor (CSL), a low cost nutrient source, for syngas fermentation to produce ethanol using Clostridium strain P11 was investigated. About 32% more ethanol (1.7 g L⁻¹) was produced with 20 g L⁻¹ CSL media in 250-mL bottle fermentations compared to media with 1 g L⁻¹ YE after 360 h. Maximum ethanol concentrations after 360 h of fermentation in a 7.5-L fermentor with 10 and 20 g L⁻¹ CSL media were 8.6 and 9.6 g L⁻¹, respectively, which represent 57% and 60% of the theoretical ethanol yields from CO. Only about 6.1 g L⁻¹ of ethanol was obtained in the medium with 1 g L⁻¹ YE after 360 h, which represents 53% of the theoretical ethanol yield from CO. The use of CSL also enhanced butanol production by sevenfold compared to YE in bottle fermentations. These results demonstrate that CSL can replace YE as the primary medium component and significantly enhance ethanol production by Clostridium strain P11.     

Techno-economic implications of improved high gravity corn mash fermentation

The performance of Saccharomyces cerevisiae MBG3964, a strain able to tolerate >18% v/v ethanol, was compared to leading industrial ethanol strain, Fermentis Ethanol Red, under high gravity corn mash fermentation conditions. Compared to the industrial ethanol strain, MBG3964 gave increased alcohol yield (140 g L⁻¹ vs. 126 g L⁻¹), lower residual sugar (4 g L⁻¹ vs. 32 g L⁻¹), and lower glycerol (11 g L⁻¹ vs. 12 g L⁻¹). After 72 h fermentation, MBG3964 showed about 40% viability, whereas the control yeast was only about 3% viable. Based on modelling, the higher ethanol tolerant yeast could increase the profitability of a corn-ethanol plant and help it remain viable through higher production, lower unit heating requirements and extra throughput. A typical 50 M gal y⁻¹ dry mill ethanol plant that sells dried distiller’s grain could potentially increase its profit by nearly $US3.4 M y⁻¹ due solely to the extra yield, and potentially another $US4.1 M y⁻¹ if extra throughput is possible.     

The physicochemical properties and chemical composition of trehalose lipids produced by Rhodococcus erythropolis 51T7

This study analyzed the chemical and physical properties of a biosurfactant synthesized by Rhodococcus sp. 51T7. The biosurfactant was a trehalose tetraester (THL) consisting of six components: one major and five minor. The hydrophobic moieties ranged in size from 9 to 11 carbons. The critical micelle concentration (CMC) was 0.037 g L⁻¹ and the interfacial tension against hexadecane was 5 mN m⁻¹. At pH 7.4 the glycolipid CMC/critical aggregation concentration (CAC) was 0.05 g L⁻¹ and at pH 4 it was 0.034 g L⁻¹. A phase diagram revealed effective emulsification with water and paraffin or isopropyl myristate. A composition of 11.3-7.5-81.8 (isopropyl myristate-THL-W) was stable for at least 3 months. The HLB was 11 and the phase behaviour of the glycolipid revealed the formation of lamellar and hexagonal liquid-crystalline textures.     

Isomerization and biodegradation of beta-cypermethrin by Pseudomonas aeruginosa CH7 with biosurfactant production

Pseudomonas aeruginosa CH7, isolated from activated sludge, was able not only to isomerize and degrade beta-cypermethrin but also to utilize it as the sole source of carbon and energy for growth and produce biosurfactant. The strain effectively degraded beta-cypermethrin with inocula biomass of 0.1-0.2 g L⁻¹ at 25-35 °C, pH 6-9, and a final concentration of beta-cypermethrin 25-900 mg L⁻¹. Via response surface methodology analysis, we found the optimal condition was 29.4 °C, pH 7.0, and inocula biomass of 0.15 g L⁻¹; under these conditions, about 90% of the beta-cypermethrin could be degraded within 12 days. Noticeably, biosurfactant was detected in the MSM culture of strain CH7, suggesting that the biosurfactant (rhamnolipid) could potentially enhance the degradation of beta-cypermethrin by promoting the dissolution, adsorption, and absorption of the hydrophobic compounds. Therefore, CH7 may serve as a promising strain in the bioremediation of wastewater and soil polluted by beta-cypermethrin.     

Alkyl-methylimidazolium ionic liquids affect the growth and fermentative metabolism of Clostridium sp

In this study, the effect of ionic liquids, 1-ethyl-3-methylimidazolium acetate [EMIM][Ac], 1-ethyl-3-methylimidazolium diethylphosphate [EMIM][DEP], and 1-methyl-3-methylimidazolium dimethylphosphate [MMIM][DMP] on the growth and glucose fermentation of Clostridium sp. was investigated. Among the three ionic liquids tested, [MMIM][DMP] was found to be least toxic. Growth of Clostridium sp. was not inhibited up to 2.5, 4 and 4 g L⁻¹ of [EMIM][Ac], [EMIM][DEP] and [MMIM][DMP], respectively. [EMIM][Ac] at <2.5 g L⁻¹, showed hormetic effect and stimulated the growth and fermentation by modulating medium pH. Total organic acid production increased in the presence of 2.5 and 2 g L⁻¹ of [EMIM][Ac] and [MMIM][DMP]. Ionic liquids had no significant influence on alcohol production at <2.5 g L⁻¹. Total gas production was affected by ILs at ?2.5 g L⁻¹ and varied with type of methylimidazolium IL. Overall, the results show that the growth and fermentative metabolism of Clostridium sp. is not impacted by ILs at concentrations below 2.5 g L⁻¹.     

Hemolymph ion regulation and kinetic characteristics of the gill (Na⁺, K⁺)-ATPase in the hermit crab Clibanarius vittatus (Decapoda, Anomura) acclimated to high salinity

We examine hemolymph ion regulation and the kinetic properties of a gill microsomal (Na⁺, K⁺)-ATPase from the intertidal hermit crab, Clibanarius vittatus, acclimated to 45‰ salinity for 10 days. Hemolymph osmolality is hypo-regulated (1102.5 ± 22.1 mOsm kg⁻¹ H₂O) at 45‰ but elevated compared to fresh-caught crabs (801.0 ± 40.1 mOsm kg⁻¹ H₂O). Hemolymph [Na⁺] (323.0 ± 2.5 mmol L⁻¹) and [Mg²⁺] (34.6 ± 1.0 mmol L⁻¹) are hypo-regulated while [Ca²⁺] (22.5 ± 0.7 mmol L⁻¹) is hyper-regulated; [K⁺] is hyper-regulated in fresh-caught crabs (17.4 ± 0.5 mmol L⁻¹) but hypo-regulated (6.2 ± 0.7 mmol L⁻¹) at 45‰. Protein expression patterns are altered in the 45‰-acclimated crabs, although Western blot analyses reveal just a single immunoreactive band, suggesting a single (Na⁺, K⁺)-ATPase α-subunit isoform, distributed in different density membrane fractions. A high-affinity (Vm = 46.5 ± 3.5 U mg⁻¹; K_0.5 = 7.07 ± 0.01 μmol L⁻¹) and a low-affinity ATP binding site (Vm = 108.1 ± 2.5 U mg⁻¹; K_0.5 = 0.11 ± 0.3 mmol L⁻¹), both obeying cooperative kinetics, were disclosed. Modulation of (Na⁺, K⁺)-ATPase activity by Mg²⁺, K⁺ and NH₄⁺ also exhibits site-site interactions, but modulation by Na⁺ shows Michaelis-Menten kinetics. (Na⁺, K⁺)-ATPase activity is synergistically stimulated up to 45% by NH₄⁺ plus K⁺. Enzyme catalytic efficiency for variable [K⁺] and fixed [NH₄⁺] is 10-fold greater than for variable [NH₄⁺] and fixed [K⁺]. Ouabain inhibited ≈80% of total ATPase activity (K_I = 464.7 ± 23.2 μmol L⁻¹), suggesting that ATPases other than (Na⁺, K⁺)-ATPase are present. While (Na⁺, K⁺)-ATPase activities are similar in fresh-caught (around 142 nmol Pi min⁻¹ mg⁻¹) and 45‰-acclimated crabs (around 154 nmol Pi min⁻¹ mg⁻¹), ATP affinity decreases 110-fold and Na⁺ and K⁺ affinities increase 2-3-fold in 45‰-acclimated crabs.     

Biotic and abiotic regulation of resting spore formation in vivo of obligate aphid pathogen Pandora nouryi: Modeling analysis and biological implication

Entomophthoralean fungus Pandora nouryi is an obligate aphid pathogen that enables to produce resting spores (azygospores) for surviving host absence. To explore possible mechanisms involved in the regulation of resting spore formation in vivo, host cohorts consisting of 40-60 nymphs of green peach aphid Myzus persicae produced within 24 h on cabbage leaf discs in petri dishes were exposed to spore showers of P. nouryi at the concentrations (C) from a very few to nearly 2000 conidia/mm² and then reared for 7-11 days at the regimes of 10-25 °C (T) and 8-16 h daylight (H_L) or ambient (17.5 ± 3.1 °C, 13:11 L:D). Aphid mortalities observed from 35-83 cohorts (showered separately) at each regime showed typical sigmoid trend and fit well a general logistic equation (0.79 ? r² ? 0.88), yielding similar LC₅₀ estimates of 1.7-6.1 conidia/mm². The proportions (P) of cadavers forming resting spores in the cohorts also fit the same equation (0.73 ? r² ? 0.85) at all tested regimes except at 10 °C, a low temperature for the host-pathogen interaction. This indicates the dependence of resting spore formation on the spore concentration. The effects of T and H_L on P over C were well elucidated by the fitted modified logistic equations P = 0.578/{1 + exp[1.710 − (0.136 − 0.0053T)C]} and P = 0.534/{1 + exp[1.639 + (0.034 − 0.0053H_L)C]} (both r² = 0.79). Our results highlight that the resting spore formation in vivo of P. nouryi is regulated primarily by the concentration of host-infecting conidia discharged from cadavers and facilitated by lower temperature and longer daylight.     

Effect of lignocellulosic inhibitory compounds on growth and ethanol fermentation of newly-isolated thermotolerant Issatchenkia orientalis

A newly isolated thermotolerant ethanologenic yeast strain, Issatchenkia orientalis IPE 100, was able to produce ethanol with a theoretical yield of 85% per g of glucose at 42 °C. Ethanol production was inhibited by furfural, hydroxymethylfurfural and vanillin concentrations above 5.56 g L⁻¹, 7.81 g L⁻¹, and 3.17 g L⁻¹, respectively, but the strain was able to produce ethanol from enzymatically hydrolyzed steam-exploded cornstalk with 93.8% of theoretical yield and 0.91 g L⁻¹ h⁻¹ of productivity at 42 °C. Therefore, I. orientalis IPE 100 is a potential candidate for commercial lignocelluloses-to-ethanol production.     

Enhanced ethanol production from sugarcane juice by galactose adaptation of a newly isolated thermotolerant strain of Pichia kudriavzevii

The thermotolerant yeast strain isolated from sugarcane juice through enrichment technique was identified as a strain of Pichiakudriavzevii (Issatchenkiaorientalis) through molecular characterization. The P. kudriavzevii cells adapted to galactose medium produced about 30% more ethanol from sugarcane juice than the non-adapted cells. The recycled cells could be used for four successive cycles without a significant drop in ethanol production. Fermentation in a laboratory fermenter with galactose adapted P. kudriavzevii cells at 40 °C resulted in an ethanol concentration and productivity of 71.9 g L⁻¹ and 4.0 g L⁻¹ h⁻¹, respectively from sugarcane juice composed of about 14% (w/v) sucrose, 2% (w/v) glucose and 1% (w/v) fructose. In addition to ethanol, 3.30 g L⁻¹ arabitol and 4.19 g L⁻¹ glycerol were also produced, whereas sorbitol and xylitol were not formed during fermentation. Use of galactose adapted P. kudriavzevii cells for ethanol production from sugarcane juice holds potential for scale-up studies.     

pH-responsive switching of near-infrared absorption of a diradical complex of Pt and 3,4-diaminobenzoate formed in aqueous solutions

In alkaline aqueous solutions, 3,4-diaminobenzoate (H₂(²L^PDA)⁻) reacts with Pt^II to form a 1:2 (Pt:L) complex that intensely absorbs near-infrared (NIR) light at 713 nm (ε = 8.0 × 10⁴ M⁻¹ cm⁻¹). The absorption disappeared at pH < 3 (in DMSO), showing pH-responsive switching of the NIR absorption. By comparing the NIR-absorbing behavior of this complex to that of a complex, [Pt^II(¹L^ISQ)₂]²⁻, containing the analogous phenylenediamine ligand [(¹L^ISQ)²⁻ = o-diiminobenzosemiquinonate radical], the complex can be formulated as [Pt^II(²L^ISQ)₂]²⁻. The assignment of the entity was consistent with the redox and spectroelectrochemical behaviors and electronic spin resonance (ESR) spectroscopy. First, one-electron oxidation of [Pt^II(²L^ISQ)₂]²⁻ formed an ESR-silent complex assignable to the dimeric complex [{Pt^II(²L^ISQ)(²L^IBQ)}₂]²⁻ [(²L^IBQ) = o-iminobenzoquinone form] in which the two radical centers at were antiferromagnetically coupled. Second, the one-electron reduced complex of [Pt^II(²L^ISQ)₂]²⁻ exhibited an ESR signal attributed to [Pt^II(²L^ISQ)(²L^PDA)]³⁻; 34% of the electronic spin was located at the Pt^II center rather than on the moiety. The pH-responsive switching-off of the NIR absorption was thus rationally explained by oxidation of [Pt^II(²L^ISQ)₂]²⁻ to [{Pt^II(²L^ISQ)(²L^IBQ)}₂]²⁻ by the increase of the rest potential of the solution in the lower pH region.