Biosorption of reactive dyes by the mycelium pellets of a new isolate of Penicillium oxalicum

Three reactive dyes were rapidly adsorbed by the mycelium pellets of Penicillium oxalicum. Dye removal of Reactive Blue 19 was up to 60% in 10 min and 91% in 80 min. Dye adsorption isotherms fitted Langmuir model well and the maximum adsorption capacities at 20 °C were calculated to be 160 mg g^–1 for Reactive Blue 19, 122 mg g^–1 for Reactive Red 241 and 137 mg g^–1 for Reactive Yellow 145, respectively. The pellets exhibited a high dye adsorption capacity (80–180 mg g^–1) for all of the 3 dyes over a wide pH range (pH 2–10), and the maximum adsorption was obtained at pH 2. The adsorption capacity was mildly increased by increasing salinity.     

Isolation of antifouling active pyroglutamic acid,triethyl citrate and di-<Emphasis Type="Italic">n</Emphasis>-octylphthalate from the brown seaweed <Emphasis Type="Italic">Ishige okamurae</Emphasis>

Three antifouling active compounds of L-pyroglutamic acid (PGA), triethyl citrate (TEC) and di-n-octylphthalate (DNOP) were isolated from the brown seaweed Ishige okamurae. Approximately 2.8 mg PGA, 1.7 mg TEC, and 2.0 mg DNOP were isolated from 600 g of I. okamurae powder. The concentrations of PGA, TEC, and DNOP required to cause foot repulsion in 50% of mussels (RD₅₀) were 9, 26, and 0.08 mM, respectively. The PGA, TEC, and DNOP concentrations required to inhibit 50% attachment of algal spores (ID₅₀) were 24, 50 and 0.1 mM, respectively. These compounds showed stable antifouling activities against mussel and algal spore attachment.     

Anions effects on biosorption of Mn(II) by extracellular polymeric substance (EPS) from Rhizobium etli

Microbial extracellular polymeric substances (EPS) are potential biosorbents for metal remediation and recovery. The Langmuir and Freundlich kinetics of Mn(II) binding by the EPS from a novel Mn(II) oxidising strain of Rhizobium etli were determined. Maximum manganese specific adsorptions (q _max) decreased in the sequence: sulphate (62 mg Mn per g EPS) > nitrate (53 mg g^–1) > chloride (21 mg g^–1). Consideration of the anion during kinetic studies is usually neglected but is important in providing more practical and comparable data between different biosorbent systems.     

Phytoplankton of shallow lakes: Seasonal succession, standing crop and the chief determinants of primary productivity, 1. Cooking Lake, Alberta, Canada

Cooking Lake (113°02′W, 53°26′N), a well-mixed, shallow (mean depth (1.59 m), eutrophic lake in Alberta, Canada, is characterized by eutrophic chlorococcalean and cyanophycean phytoplankton associations, and little change in standing crop with increasing depth. Standing crop and primary productivity are low during the winter but pronounced spring and summer maxima occur. Mean yearly areal standing crop (ΔB) and primary productivity (ΔA) were 212.4 mg m^?2 chlorophyll a and 301.8 mg C h^?1 m^?2 respectively. Annual productivity was estimated at 1322 g C m^?2. The mean increase in the extinction coefficient (?) per unit increase in standing crop (B) was 0.03 In units m^?1. High non-algal light attenuation (?_q) occurred avenging 41 which prevented the ratio B/? from attaining more than 65% of the theoretical maximum except once when algal self-shading occurred. Close correlations existed between B (mg m^?3 chlorophyll a) and A _max (mg h_?1 m_?3) ΔA and ΔB, ΔA and B, A_max, and A_max/?, and ΔA and I_o′, (W m^?2). The depth of the euphotic zone (Z_eu) varied between 0.5 and 1 25 m; the average relationship between z_eu and E was Z_eu= 3.74/?, and the mean standing Crop found in the euphotic zone represented 55.2% of the theoretical maximum, The high ?_q, values made the model of Tailing (1957) inapplicable to Cooking Lake. The Q₁₀ value for the lake was 2.2. The maximum rate of photosynthesis per unit of population per h. Ø^max, (mg C sag chlorophyll a_?1 h_?1) was more closely related to temperature than irradiance and ma depressed by pH values greater than 9.1. Growth of the phytoplankton was not nutrient limited: instead irradiance and temperature were more important. Indirect evidence that free CO₂ limited photosynthetic rates, is provided by the Ø_max: pH relationship.     

Effect of irradiance during growth of Glycine max on photosynthetic capacity and percent activation of ribulose 1,5-bisphosphate carboxylase

The initial (in vivo) and total (activity present after preincubation with CO₂ and Mg²⁺) activities of ribulose bisphosphate carboxylase were both assayed in extracts of leaves of soybean (Glycine max) plants which had been grown under 4 different irradiance levels. The total carboxylase activity per unit leaf area decreased with decreased irradiance during growth but was not different on a dry weight basis. The initial activity as a percentage of the total activity was unchanged (approximately 95%) except in leaves of plants grown at the lowest irradiance (74%). When the plants grown at the lowest irradiance were exposed to high irradiance, the initial activity was increased to 93% of the total. Light saturated rates of photosynthesis per unit leaf area were lower and saturated at lower irradiance for plants grown at lower irradiances. Initial carboxylase activity was correlated closely (r²=0.84) with leaf photosynthesis rate on a dry weight basis.     

Adsorption of cellulase fromTrichoderma viride on microcrystalline cellulose

Summary The adsorption behaviour of cellulase fromTrichoderma viride on microcrystalline celluloses with different specific surface areas was studied. The adsorption was found to fit a Langmuir isotherm. There was an increase in the maximum adsorption amount (A_max) as the specific surface area of microcrystalline cellulose increased. The values of A_max and adsorption equilibrium constant (K) decreased with increasing temperature. Thermodynamic parameters in adsorption were calculated from K. It was found from the enthalpy of adsorption, that van der Waals-Type interaction was responsible for adsorption of cellulase on microcrystalline cellulose. The adsorption process was exothermic and an adsorption enthalpy-controlled reaction.     

Length–weight relationship and a relative condition factor equation for lake sturgeon (Acipenser fulvescens) from the St Clair River system (Michigan, USA)

Several USA state, federal, and Canadian agencies study lake sturgeon (Acipenser fulvescens) within the St Clair River and Lake St Clair, collectively referred to hereafter as the St Clair River (SCR) system. Previously, there has been no set standard for determining condition for SCR system lake sturgeon. Condition measures the variation from the expected weight for length as an indicator of fatness, general well‐being, gonad development, etc. The aim of this project was to determine the length–weight relationship of lake sturgeon caught from the SCR system, from which a relative condition factor (K_n) equation could be derived. Total length (TL, mm) and weight (W, kg) were measured for 1074 lake sturgeon (101 males and 16 females were identifiable) collected by setline and bottom trawl from the SCR system in May–September, 1997–2002. Analysis of covariance found no difference in the length–weight relationship between sampling gear or sex. Least‐squares regression of log₁₀W × log₁₀TL produced the overall equation logW = 3.365logTL ? 9.320. Using the exponential form of the slope and y‐intercept, relative condition factor for lake sturgeon from the SCR system can be calculated as K_n = W/[(4.786 × 10^?10)(TL^3.365)]. Equations for males and females were also developed. Overall, body condition was significantly correlated with both age and girth; no significant difference in K_n by sex was found. In general, the SCR lake sturgeon population was near the upper ends of growth and condition ranges listed in the literature, comparable with those populations that are at similar latitudes. Although condition factors should be interpreted with caution, proper use of a standard equation provides a non‐lethal measure of overall fish health that can be used by biologists and managers in ongoing efforts to restore lake sturgeon throughout the Great Lakes.     

The effects of oxygen levels on oxygen consumption, survival and ventilatory frequency of sharpsnout sea bream (Diplodus puntazzo Gmelin, 1789) at different conditions of temperature and fish weight

The respiratory behaviour of the sharpsnout sea bream (Diplodus puntazzo) with fish weights between 15 and 509 g at temperatures of 15–29°C was studied, with special attention paid to critical and lethal oxygen saturation (S_crit and LC₅₀, respectively) and ventilatory frequency (V_f). The species maintained a constant oxygen consumption rate regardless of the concentration of dissolved oxygen, until S_crit was reached. The mean of S_crit and LC₅₀ was 34% (2.4 mg L⁻¹) and 11% (0.8 mg L⁻¹), respectively. The S_crit was independent of fish weight and temperature, whereas the LC₅₀ values were positively correlated with both factors (P < 0.05). The higher resistance in small fish could be due to their greater V_f response to hypoxia than in larger animals. Furthermore, the increased metabolism resulting from the effect of temperature was offset by an increased V_f. The V_f remained constant down to a mean value of 67% oxygen saturation, regardless of fish weight and temperature. These findings suggest an optimum oxygen saturation of above 70% for D. puntazzo culture.     

Effects of UV-B radiation on growth rates,pigment content and ultrastructure of red (wild type), greenish-brown and green strains of Gracilaria birdiae (Gracilariales,Rhodophyta)

Based on physiological characteristics, we hypothesized that different strains of Gracilaria birdiae from two distinct geographical areas of the Brazilian coast (2500 km apart) would have different responses to long-term exposure to UV-B radiation (UV-B). The locations differ in their environmental conditions: one is a warmer area, Ceará State (CE), closer to the equator; the other is a colder area, Espirito Santo State (ES), closer to the Tropic of Capricorn. To test the hypothesis that the CE population is more resistant to UV-B than the ES population, apical segments of the red (RD_CE, RD_ES), green (GR_CE) and greenish-brown (GB_CE) strains were cultivated in the laboratory under two treatments: control (PAR) and artificial UV-B (PAR + UV-B). Algal performance was evaluated by considering growth rates, pigment content and ultrastructural analysis. Compared with the control, all strains showed a decrease in growth rates after exposure to UV-B. Of all strains, RD_ES showed the greatest sensitivity to UV-B. However, a decrease in growth rate and morphological changes were observed to a lesser extent in the RD_CE strain. Moreover, exposure to UV-B resulted in a decrease in the concentrations of phycobiliproteins in the RD_CE strain. The GB_CE strain showed an increase in phycoerythrin (PE)/allophycocyanin (APC) and phycocyanin (PC)/allophycocyanin (APC) ratios after exposure to UV-B, suggesting this strain had a higher tolerance to the radiation. No differences in the chlorophyll a and carotenoid content were found between the control and UV-B treated samples for all strains. Ultrastructural changes, such as damage to chloroplasts and mitochondria, were present in all strains after exposure to UV-B. In summary, our findings support the hypothesis that the population from Ceará State has adapted to the higher irradiation and is thus more resistant to increased UV-B. Additionally, of the strains tested, the GB_CE and RD_CE strains appear to be more resistant to this radiation.     

Effects of leaf position and nitrogen supply on the expansion of leaves of field grown sunflower (Helianthus annuus L.)

Leaf growth responses to N supply and leaf position were studied using widely-spaced sunflower plants growing under field conditions. Both N supply (range 0.25 to 11.25 g added N per plant) and leaf position significantly (p=0.001) affected maximum leaf area (LA_max) of target leaves through variations in leaf expansion rate (LER); effects on duration of expansion were small. Specific leaf nitrogen (SLN, g N m^-2) fell quite rapidly during the initial leaf expansion phase (LA < 35% LA_max) but leveled off during the final 65% increase of leaf area. This pattern held across leaf positions and N supply levels. Leaf nitrogen accumulation after 35% LA_max continued up to achievement of LA_max; reductions in the higher SLN characteristic of the initial phase were insufficient to cover the nitrogen requirements for expansion during the final phase. LER in the quasi-linear expansion phase (35 to 100% of LA_max) was strongly associated with SLN above a threshold that varied with leaf position (mean 1.79±0.225 g N m^-2). This contrasts with the response of photosynthesis at high irradiance to SLN, which has previously been shown to have a threshold of 0.3 g N m^-2; in the present work saturation of photosynthetic rate was evident when SLN reached 1.97 g N m^-2. Thus, once the area of a leaf exceeds 35% of LA_max, expansion proceeds provided SLN values are close to the levels required for maximum photosynthesis. However, growth of leaves during the initial expansion phase ensures a minimum production of leaf area even at low N supply levels.     

Acclimation to humic substances prevents whole body sodium loss and stimulates branchial calcium uptake capacity in cardinal tetras Paracheirodon axelrodi (Schultz) subjected to extremely low pH

Kinetics of sodium (Na⁺) and calcium (Ca²⁺) uptake were studied in cardinal tetras Paracheirodon axelrodi acclimated to humic substances (HS, 35 mg C l^?1) and low pH (pH 3·72), parallel to analysis of whole body Na⁺ and Ca²⁺ content. This species had a high uptake capacity (J_max) for both Na⁺ and Ca²⁺ in soft, ion‐poor water. The affinity constant (K_m) did not vary significantly among treatments for either Na⁺ or Ca²⁺. J_max Na⁺ increased 30% in fish acclimated to HS for 5 weeks. Acclimation to low pH had no effect on J_max Na⁺ but this treatment was associated with a 32% decrease on whole body Na⁺ content, suggesting that fish were unable to compensate for the increased Na⁺ loss induced by extreme acidity. Exposure of fish to HS + low pH, the treatment most closely approximating to the conditions experienced by the species in its native environment, resulted in an increase in whole body Na⁺ by 31% relative to acclimation to low pH alone. J_max Ca²⁺ in cardinal tetras was high relative to that documented in other freshwater species acclimated to soft water (J_max= 30 nmol g^?1 h^?1). Prolonged exposure of fish to pH 3·72 inhibited J_max Ca²⁺ by 53%, although whole body Ca²⁺ content remained unchanged relative to control. Acclimation of fish to HS + low pH resulted in an increase of J_max Ca²⁺ by 166% relative to low pH alone. Collectively, these results suggest that HS protect cardinal tetras acclimated to soft, acidic waters by preventing excessive Na⁺ loss (as indicated by whole body Na⁺ content) and by stimulating Ca²⁺ uptake (as indicated by increased J_max Ca²⁺) to ensure proper homeostasis.     

Influence of body weight/age on the food intake,growth and conversion efficiency of Gambusia affinis

On a restricted food supply of Tubifex tubifex (2h/day) the fish consumed only 69.5 mg dry food/g live fish/day and grew only to 25.6 mg live body weight by the 30th day of it's age, while those fed ad libitum consumed 94.7 mg/g/day and attained a body weight of 125.9 mg live weight by the 30th day. Conversion efficiency (K₁) averaged to 8.3% in the former and 14.1% in the latter series, throughout the 30 day experimental period.Feeding rate of the test series fed individually and at ad libitum, decreased from 780 mg dry food/g dry fish/day for a fish weighing 4 mg dry weight to 180 mg/g/ day for one weighing 41 mg, exhibiting a log-log relationship to the body weight (Y = 2.20140–0.5639 X). Growth rate also decreased as a log-log function with increasing body weight (Y = 1.2309–0.4384 X).     

Purification and characterization of x-prolyl-dipeptidyl aminopeptidase from Lactococcus lactis subsp. cremoris NRRL 634

Summary An X-prolyl-dipeptidylaminopep tidase (Pep-XP) was purified from the crude intracellular extract of Lactococcus lactis subsp. cremoris NRRL 634 by ion exchange and gel filtration chromatographies. The enzyme was purified 80-fold with a recovery of 6%, and appeared as a single band with a molecular weight of about 80 kDa on polyacrylamide gel electrophoresis with sodium dodecyl sulphate (SDS-PAGE). The peptidase showed its maximal activity on arginyl-proline-p-nitroanilide at pH 7.0 and at a temperature of 45 °C, although there was a good activity of Pep-XP in the pH range of 5.5–7.0 and temperatures between 40 and 50 °C. The Michaelis constant (K _m) and the maximum reaction velocity (V _max) values were 0.92 mM and 7.9 U/mg protein min, respectively. The activity of Pep-XP was completely inhibited by phenylmethanesulphonyl fluoride, an inhibitor of serine peptidases, and metal chelators had little effect on enzyme activity. The purified enzyme hydrolyzed synthetic substrates whose structure is X-Pro-Y like Lys-Pro-pNA, but did not hydrolyse Pro-pNA or azocasein, showing that the enzyme did not have aminopeptidase or endopeptidase activities.     

Immobilization of Candida rugosa lipase on sporopollenin from Lycopodium clavatum

Sporopollenin is a natural polymer obtained from Lycopodium clavatum, which is highly stable with constant chemical structure and has high resistant capacity to chemical attack. In this study, immobilization of lipase from Candida rugosa (CRL) on sporopollenin by adsorption method is reported for the first time. Besides this, the enzyme adsorption capacity, activity and thermal stability of immobilized enzyme have also been investigated. It has been observed that under the optimum conditions (Spo-E_(0.3)), the specific activity of the immobilized lipase on the sporopollenin by adsorption was 16.3 U/mg protein, which is 0.46 times less than that of the free lipase (35.6 U/mg protein). The pH and temperature of immobilized enzyme were optimized, which were 6.0 and 40 °C respectively. Kinetic parameters V_max and K_m were also determined for the immobilized lipase. It was observed that there is an increase of the K_m value (7.54 mM) and a decrease of the V_max value (145.0 U/mg-protein) comparing with that of the free lipase.     

Photosynthetic and gas exchange characteristics of dominant woody plants on a moisture gradient in an African savanna

We determined key photosynthetic gas exchange parameters, and their temperature dependence, in dominant woody plants at four savanna sites on a moisture gradient in Botswana, southern Africa. Leaf stable carbon and nitrogen (N) isotope and morphological measures were made concurrently. Sampling of these predominantly non‐N‐fixing species took place during an exceptional rainfall season, representing near‐optimum conditions for primary production at these sites. The mean specific leaf area and leaf size were positively related to mean annual rainfall (MAR); species with larger leaves of lower density were more abundant in wetter sites. Almost all species at all sites showed high net light‐saturated photosynthetic rates (A_max?10 μmol CO₂ m^?2 s^?1) due both to high CO₂ carboxylation (V_c,max) and RubP‐regeneration capacity (J_max). These high rates were associated with high values of leaf [N]. Across all sites, the temperature response of A_max showed no clear optimum, and a gradual drop from 25°C to 35°C, without notable temperature limitation at leaf temperatures in excess of 35°C. Dark respiration rate (R_day) across all species and sites increased exponentially with increasing leaf temperature. Species sampled at selected sites revealed a negative relationship between leaf δ¹³C (stable carbon isotope ratio) and MAR, suggesting higher leaf‐level water‐use efficiency at drier sites when integrated over the life of the leaf. At wetter sites, specific leaf [N] was lower and photosynthetic nitrogen‐use efficiency increased, a pattern reflected at the ecosystem level by less ¹⁵N enrichment of leaves at these sites. Taken together, the results suggest a switch from water‐use to nitrogen‐use efficiency constraints with increasing moisture availability. These constraints impact leaf form and function significantly, and may emerge at the ecosystem level in aspects of water and N cycling.     

Feeding and growth of juvenile sea bass: the effect of ration and temperature on growth rate and efficiency

The effect of ration on the growth of pairs of juvenile sea bass Dicentrarchus labrax fed squid mantle was recorded at four temperatures: 6, 10, 14 and 18) C, covering the range typical of Welsh coastal waters. Initial weight of the fish ranged from 2.8 to 15.9 g. A predictive model for the maximum meal size (M_max) at temperatures between 10 and 18) C, accounted for 95% of the variance in lnM_max. Even when offered excess food, bass at 6) C had a low rate of food consumption [0.19% body weight (BW) day^?1] and lost weight (G=?0.04% day^?1). Predictive regression models for specific growth rate (G) accounted for 86% of the variance at reduced rations and 70% at maximum meals. The relationship between G (calculated for total biomass per tank) and ration was a decelerating curve. G at maximum meals increased with temperature, at lower rations G decreased with temperature. For a pair of bass with a combined weight of 15 g, predicted maintenance ration ranged between 0.7 and 2.3% BW day^?1 and increased with temperature. Maximum meal size was more sensitive to temperature than maintenance ration. At 18) C optimum ration was 7.4% BW day^?1. At lower temperatures, the optimum ration was the maximum meal. The maximum gross growth efficiency was 17.4% at 18) C. Mean absorption efficiency was 94.8%. Ration level had no significant effect on absorption efficiency, which was lowest at 6) C. Condition indices (Fulton condition factor, wet and dry liver—somatic indices and body depth index) increased with meal size at all temperatures except 6) C. An increase in temperature between 10 and 18) C generally resulted in a decrease in condition indices at a given ration. When comparisons were made at a given standard length, gut and carcass weight increased with ration. Visceral fat and gut weight decreased with increased temperature.     

Sub-lethal temperature thresholds indicate acclimation and physiological limits in brook trout Salvelinus fontinalis

The upper thermal tolerance of brook trout Salvelinus fontinalis was estimated using critical thermal maxima (CT_max) experiments on fish acclimated to temperatures that span the species' thermal range (5–25°C). The CT_max increased with acclimation temperature but plateaued in fish acclimated to 20, 23 and 25°C. Plasma lactate was highest, and the hepato-somatic index (I_H) was lowest at 23 and 25°C, which suggests additional metabolic costs at those acclimation temperatures. The results suggest that there is a sub-lethal threshold between 20 and 23°C, beyond which the fish experience reduced physiological performance.     

Distribution,abundance, and feeding of a disjunct population of lady crab in the southern Gulf of St. Lawrence,Canada

The lady crab (Ovalipes ocellatus) is one of the most common native species of swimming crab (Portunidae) of the Atlantic Coast of North America but most populations occur south of Cape Cod, Massachusetts. There is a disjunct population in Northumberland Strait (southern Gulf of St Lawrence), which was the focus of this study. Adult lady crabs were collected by trawling in water >4 m deep from May to October 1999 to 2005 to determine abundance, distribution, and diet. Lady crab occurred only in a small area (about 2,500 km²) in the central part of Northumberland Strait where bottom water temperature was >18°C during summer, and the substrate was mainly sand or sandy gravel. Male lady crab attained a maximum carapace width (CW) of 112 mm compared to 92 mm CW for females. The summer and autumn diet consisted mainly of infauna. The principal prey (each >5% of diet by weight) were: small bivalve molluscs (primarily Atlantic razor clam Siliqua costata and Macoma sp.; 43%), small rock crab (Cancer irroratus; 13%), polychaetes (11%), fish remains (9%), and small lady crab (9%). All stomachs collected during May (water temperature ≤10°C) were empty. There was little evidence of any difference in feeding intensity between 0700 h and 1900 h.     

Mixed substrate growth of methylotrophic yeasts in chemostat culture: Influence of the dilution rate on the utilisation of a mixture of glucose and methanol

The growth of Hansenula polymorpha and Kloeckera sp. 2201 with a mixture of glucose and methanol (38.8%/61.2%, w/w) and the regulation of the methanol dissimilating enzymes alcohol oxidase, catalase, formaldehyde dehydrogenase and formate dehydrogenase were studied in chemostat culture, as a function of the dilution rate. Both organisms utilized and assimilated glucose and methanol simultaneously up to dilution rates of 0.30 h^-1 (H. polymorpha) and 0.26h^-1, respectively (Kloeckera sp. 2201) which significantly exceeded _max found for the two yeasts with methanol as the only source of carbon. At higher dilution rates methanol utilisation ceased and only glucose was assimilated. Over the whole range of mixed-substrate growth both carbon sources were assimilated with the same efficiency as during growth with glucose or methanol alone.In cultures of H. polymorpha, however, the growth yield for glucose was lowered by the unmetabolized methanol at high dilution rates. During growth on both carbon sources the repression of the synthesis of all catabolic methanol enzymes which is normally caused by glucose was overcome by the inductive effect of the simultaneously fed methanol. In both organisms the synthesis of alcohol oxidase was found to be regulated differently as compared to catalase, formaldehyde and formate dehydrogenase. Whereas increasing repression of the synthesis of alcohol oxidase was found with increasing dilution rates as indicated by gradually decreasing specific activities of this enzyme in cell-free extracts, the specific activities of this enzyme in cell-free extracts, the specific activities of catalase and the dehydrogenases increased with increasing growth rates until repression started. The results indicate similar patterns of the regulation of the synthesis of methanol dissimilating enzymes in different methylotrophic yeasts.Abbreviations and Terms C₁ Methanol - C₆ glucose; D dilution rate (h^-1) - D _c critical dilution rate (h^-1) - q _s specific, rate of substrate consumption (g substrate [g cell dry weight]^-1 h^-1) - q _CO2 and q _O2 are the specific rates of carbon dioxide release and oxygen consumption (mmol [g cell dry weight]^-1 h^-1) - RQ respiration quotient (q _CO2 q _O2 ¹ ) - s ₀(C₁) and s ₀(C₆) are the concentrations of methanol and glucose in the inflowing medium (g l^-1) - s residual substrate concentration in the culture liquid (g l^-1) - Sp. A. enzyme specific activity - x cell dry weight concentration (gl^-1) - Y _X/C6 growth yield on glucose (g cell dry weight [g substrate]^-1     

Decolorization of melanin by lignin peroxidase from<Emphasis Type="Italic">Phanerochaete chrysosporium</Emphasis>

Melanin was decolorized by lignin peroxidase fromPhanerochaete chrysosporium. This decolorization reaction showed a Michaelis-Mentens type relationship between the decolorization rate and concentration of two substrates: melanin and hydrogen peroxide. Kinetic constants of the decolorization reaction were 0.1 OD₄₇₅/min (V _max) and 99.7 mg/L (K _m) for melanin and 0.08 OD₄₇₅/min (V _max) and 504.9 μM (K _m) for hydrogen peroxide, respectively. Depletion of hydrogen peroxide interrupted the decolorization reaction, indicating the essential requirement of hydrogen peroxide. Pulsewise feeding of hydrogen peroxide continued the decolorizing reaction catalyzed by lignin peroxidase. These results indicate that enzymatic decolorization of melanin has applications in the development of new cosmetic whitening agents.