Liquid–liquid extraction of levulinic acid from aqueous solutions using hydrophobic tri-n-octylamine/alcohol-based deep eutectic solvent

Levulinic acid(LA)is one of the top-12 most promising biomass-based platform chemicals,which has a wide range of applications in a variety of fields.However,separation and purification of LA from aqueous solution or actual hydrolysate continues to be a challenge.Among various downstream separation technologies,liquid-liquid extraction is a low-cost,effective,and simple process to separate LA.The key breakthrough lies in the development of extractants with high extraction efficiency,good hydrophobicity,and low cost.In this work,three hydrophobic deep eutectic solvents(DESs)based on tri-n-octylamine(TOA)as hydrogen bond acceptor(HBA)and alcohols(butanol,2-octanol,and menthol)as hydrogen bond donors(HBDs)were developed to extract LA from aqueous solution.The molar ratios of HBD and HBA,extraction temperature,contact time,solution pH,and initial LA concentration,DES/water volume ratios were systematically investigated.Compared with 2-octanol-TOA and menthol-TOA DES,the butanol-TOA DES exhibited the superior extraction performance for LA,with a maximum extraction efficiency of 95.79±1.4%.Moreover,the solution pH had a great impact on the LA extraction efficiency of butanol-TOA(molar ratio=3:1).It is worth noting that the extraction equilibrium time was less than 0.5 h.More importantly,the butanol-TOA(3:1)DES possesses good extraction abilities for low,medium,and high concentrations of LA.

Selectively reductive amination of levulinic acid with aryl amines to N-substituted aryl pyrroles

Synthesizing nitrogen(N)-containing molecules from biomass derivatives is a new strategy for production of this kind of chemicals.Herein,for the first time we present the synthesis of N-substituted aryl pyrroles via reductive amination/cyclization of levulinic acid(LA)with primary aromatic amines and hydrosilanes(e.g.,PMHS)over Cs F,and a series of N-substituted aryl pyrroles could be obtained in good to excellent yields at 120○C.The mechanism investigation indicates that the reaction proceeds in two steps:the cyclization between amine and LA occurs first to form intermediate 5-methyl-N-alkyl-1,3-dihydro-2H-pyrrolones and their isomeride(B),and then the chemo-and region-selective reduction of intermediates take place to produce the final products.This approach for synthesis of N-substituted aryl pyrroles can be performed under mild and green conditions,which may have promising applications.

Esterification of levulinic acid to n-butyl levulinate over heteropolyacid supported on acid-treated clay

Levulinic acid has been identified as a promising green, biomass-derived platform chemical. n-Butyl levulinate is used as an important intermediate having diverse applications. The present work focuses on the synthesis of n-butyl levulinate by esterification of levulinic acid with n-butanol using heteropolyacid （HPA） supported on acid-treated clay montmorillonite （K10）. 20% （w/w） dodecatungestophosphoric acid （DTPA） supported on K10 was found to be the most efficient catalyst with 97% levulinic acid conversion and 100% selectivity towards n-butyl levulinate. Effects of various process parameters were studied to examine the efficacy of 20% （w/w） DTPA/K10 for optimization of the activity.

In situ synthesis of biomass-derived Ni/C catalyst by self-reduction for the hydrogenation of levulinic acid to γ-valerolactone

Herein,we reported in situ synthesis of biomass-derived Ni/C catalyst by self-reduction with pomelo peel.Compared with the conventional method, which includes carbonization, activation, impregnation and reduction, the entire preparation process was simplified to two steps, which was more straightforward. This synthesis method was green as Ni/C can be prepared without any additional chemical and the self-reduction process was realized in N2, which can avoid using H2 thus averting some problems such as storage, transportation and safety of H2. Meanwhile, the size and dispersion of Ni particles can be controlled by changing carbonization temperature.The synthesis mechanism of Ni/C catalyst with selfreduction was investigated, which was mainly attributed to the carbon and reducing gas produced during the carbonization process.For the catalytic performance of GVL synthesis, a high yield (94.5%) can be obtained and it exhibited good stability up to 5 cycles without obvious loss of catalytic activity.

Role of the Cu-ZrO_(2) interface in the hydrogenation of levulinic acid to γ-valerolactone

Here we exquisitely fabricated Cu/ZrO_(2)-dp catalysts with plentiful Cu-ZrO_(2)interfaces by depositing amorphous ZrO_(2)onto Cu nanoparticles for the hydrogenation of levulinic acid(LA)to y-valerolactone(GVL).With the created plentiful CU-ZrO_(2)interfaces,the optimal catalyst 3 Cu/ZrO_(2)-dp exhibited exceptional catalytic performance under mild reaction conditions,and achieved the highest GVL mass productivity of 266.0 mmol GVL·h^(-1)·g^(-1)Cu,which was 12.5 and 2.3 times of CU/ZrO_(2)catalysts with equivalent Cu loadings prepared by traditional impregnation(3 Cu/ZrO_(2)-im)or co-precipitation(3 Cu/ZrO_(2)-cp).As far as we know,this GVL mass productivity stood at the highest level compared with those obtained using non-noble metal catalysts under similar reaction conditions.By systematic investigation with multiple characterizations,density functional theory(DFT)calculations,and kinetic studies,it was found that interfacial active centers were created at Cu-ZrO_(2)interfaces,which contained oxygen vacancies(O_(v)),negatively charged Cu^(δ)-and partially reduced Zr^(3+)The O_(v) favored the adsorption and activation of LA via its ketone group,while negatively charged Cu^(δ)-was able to enhance heterolysis of H2,which resulted in the formation of H^(+)-Cu^(δ)-and Zr^(3+)-H^(-)active species via hydrogen spillover.Also,plentiful acid sites,which derived from coordinatively unsaturated and defective Zr species,generated at Cu-ZrO_(2)interfaces.With the cooperation of interfacial active centers(Cu^(δ-)-O_(v)-Zr^(3+))and acid sites,the fabricated 3 Cu/ZrO_(2)-dp with plentiful Cu-ZrO_(2)interfaces achieved excellent catalytic performance for the hydrogenation of LA to GVL.Hence,the synergistic catalysis of Cu-ZrO_(2)interfaces provided an effective strategy for designing catalysts with a satisfactory performance for the hydrogenation of LA,which also can be expanded to other hydrodeoxygenation reactions.

Aqueous-phase hydrogenation of levulinic acid over carbon layer protected silica-supported cobalt-ruthenium catalysts

The hydrogenation of levulinic acid(LA)to c-valerolactone(GVL)by using water as solvent is a crucial process in the production of fine chemicals from biomass.An ultrathin carbon layer coating CoRu bimetallic catalyst supported on silica(CoRu@C/SiO2)is prepared by using tannis-ligated cobalt-ruthenium complex on silica as precursors,and applied for catalyzed synthesis of GVL from LA.Because of the synergistic effect between cobalt and ruthenium,the addition of small amounts of Ru to Co catalysts can increase the catalytic activity in the aqueous hydrogenation of LA.The ultrathin carbon layer covered on the CoRu bimetallic catalyst can greatly reduce the leaching of active metals.The CoRu@C/SiO2 catalyst achieves high stability and is reused up to 5 runs without significant loss of performance in aqueous hydrogenation of levulinic acid.

The hydrogenation of levulinic acid to γ-valerolactone over Cu–ZrO2 catalysts prepared by a pH-gradient methodology

A novel pH gradient methodology was used to synthesise a series of Cu–ZrO2 catalysts containing different quantities of Cu and Zr.All of the catalysts were highly selective to the desired product,γ-valerolactone, and are considerably more stable than Cu–ZrO2 catalysts prepared by other co-precipitation methods for this reaction.Characterisation and further investigation of these catalysts by XRD, BET, SEM and XPS provided insight into the nature of the catalytic active site and the physicochemical properties that lead to catalyst stability.We consider the active site to be the interface between Cu/CuOxand ZrOx and that lattice Cu species assist with the dispersion of surface Cu through the promotion of a strong metal support interaction.This enhanced understanding of the active site and roles of lattice and surface Cu will assist with future catalyst design.As such, we conclude that the activity of Cu–ZrO2 catalysts in this reaction is dictated by the quantity of Cu–Zr interface sites.

Co encapsulated N-doped carbon nanotubes as robust catalyst for valorization of levulinic acid in aqueous media

The construction of an acid resistant catalyst for synthesis of γ-valerolactone from levulinic acid in aqueous media is an important but highly challenging goal.Herein,an efficient Co@NCNT-800(after 800℃ pyrolysis) catalyst was constructed by confining Co in N-doped carbon nano-tubes(NCNT) from low cost materials by a facile strategy.Combined with the characterization results and control experiments,the in situ formed Co and Co-Ox, but not Co-Nx, proved to be the main synergistic active sites of the catalyst.It was also found that Co species are completely isolated within the bamboo-like NCNT,which could protect the metal nanoparticles from agglomeration and leaching in the strong acid reaction system.The γ-valerolactone yield of no less than 99.9% can be obtained under a relatively mild condition,and the catalytic performance has not been significantly reduced within five cycles.Therefore,this work may pave a way for the design of robust non-noble catalyst,and has potential for the production of γ-valerolactone from biomass in large-scale industries.

Preliminary Optimization and Kinetics of SnCl_(2)-HCl Catalyzed Hydrothermal Conversion of Microcrystalline Cellulose to Levulinic Acid

Levulinic acid(LA)is a platform biorefinery chemical from biomass which can be converted to green solvents,plasticizers,polymer precursors,biobased cleaning agents,fuels and fuel additives.This study assessed the potential of SnCl_(2)-based mixed acid systems as catalyst in the hydrothermal conversion of microcrystalline cellulose to levulinic acid.Maximum LAyield of 36.2 mol%was achieved using 0.2 M SnCl_(2) concentration at test conditions of 3 h,180℃ and 1%w/v cellulose loading.To reduce precipitate formation and further improve LA yield,the strategy employed was to combine SnCl_(2)(a Lewis acid)with conventional mineral acids(Bronsted acids).Evaluation of the catalytic performance of SnCl_(2)-HCl,SnCl_(2)-H_(2)SO_(4),SnCl_(2)-HNO_(3),and SnCl_(2)-H_(3)PO_(4)(1:1 molar ratio,0.2 M total acid concentration)were done with highest LA yield of 47.0 mol%obtained using the SnCl_(2)-HCl system at same test conditions.Response surface methodology optimization employing Box-Behnken design generated a quadratic model with a high coefficient of determination(r2)of 0.964.A maximum LA yield of 63.5 mol%can be achieved at 0.17 M catalyst concentration,198℃,and 5.15 h reaction time.Rate constants were estimated using nonlinear regression,while activation energies were determined using Arrhenius equation.Cellulose hydrolysis was determined to be the rate-limiting step in the overall process.Low activation energy of 63.3 kJ/mol for glucose dehydration to hydroxymethylfurfural supports the action of SnCl_(2) as Lewis acid in the mixed-acid system.LA yield simulations for plug flow reactor(PFR)and continuous stirred tank reactor(CSTR)were done suggesting a similar PFR-CSTR configuration with the established Biofine process.Lastly,a reaction scheme was presented to explain the synergy between SnCl_(2) and HCl in LA production from cellulose.

Highly active and stable Co nanoparticles embedded in nitrogen-doped mesoporous carbon nanofibers for aqueous-phase levulinic acid hydrogenation

Developing a highly active and durable non-noble metal catalyst for aqueous-phase levulinic acid(LA)hydrogenation to g-valerolactone(GVL)is an appealing yet challenging task.Herein,we report well-dispersed Co nanoparticles(NPs)embedded in nitrogen-doped mesoporous carbon nanofibers as an efficient catalyst for aqueous-phase LA hydrogenation to GVL.The Co zeolitic imidazolate framework(ZIF-67)nanocrystals were anchored on the sodium dodecyl sulfate modified wipe fiber(WF-S),yielding one-dimensional(1-D)structured composite(ZIF-67/WF-S).Subsequently,Co NPs were uniformly embedded in nitrogen-doped mesoporous carbon nanofibers(Co^(R)NC/SMCNF)through a pyrolysis-reduction strategy using ZIF-67/WF-S as the precursor.Benefiting from introducing modified wipe fiber WF-S to enhance the dispersion of Co NPs,and Co^(0) with Co-N_xdual active sites,the resulting Co^(R)NC/SMCNF catalyst shows brilliant catalytic activity(206 h^(-1) turnover frequency).Additionally,the strong metal-support interactions greatly inhibited the Co NPs from aggregation and leaching from the mesoporous carbon nanofibers,and thus increasing the reusability of the Co^(R)NC/SMCNF catalyst(reusable nine times without notable activity loss).

Enzymatic Conversion of Biobased Levulinic Acid into an Alternative Biofuel Candidate--Methyl Levulinate

Methyl levulinate(ML)is a promising green candidate for bio-based diesel fuel and fuel additives.An efficient enzyme-catalyzed process to synthesize ML from levulinic acid(LA)in methanol was developed.The catalytic activity of a series of lipases including Novozyme 435(N435),NRTL IM,and 40086 was screened,and the N435 was identified as the optimal biocatalyst for the process.The effects of lipase amount,methyl tert-butyl ether(MTBE)volume,methanol to LA molar ratio,reaction temperature,and magnetic stirrer speed on LA conversion and ML yield were investigated.The response surface methodology was adopted to optimize the enzymatic conversion process,and the model validation experiments showed that the predicted values corresponded well with the experimental values.A LA conversion of 90.1%and a ML yield of 89.8%were achieved under reaction conditions covering:a temperature of 45°C,a reaction time of 4.6 h,a N435 dosage of 26 mg,a methanol to LA molar ratio of 3.6:1,a MTBE volume of 3.85 mL,and a stirrer speed of 150 r/min.The N435 recycling experiment indicated that the lipase activity was quite high after 12 cycles.However,upon using crude LA prepared from carbohydrates as the reactant,the conversion of LA and the ML yield decreased due to impurities existing in the crude LA.

Hydrogen production from steam reforming of biomass-derived levulinic acid over highly stable spinel-supported Ni catalysts

As one of the main oxygen-containing organic products generated from the hydrothermal conversion of biomass,levulinic acid(LA)has the potential to be further upgraded.This work investigated the steam reforming(SR)process of biomass-derived LA to produce H_(2).A series of Ni catalysts supported by various spinels were synthesized via co-precipitation and impregnation.The Ni active metal dispersed well on the NiAl_(2)O_(4)catalyst with high specific surface area,thereby exhibiting high catalytic activity.Among all the catalysts tested,15Ni/NiAl_(2)O_(4)showed the best performance for SR of LA,resulting in high carbon conversion of 96.3%,H_(2)yield of 92.8%,and H_(2)concentration of 67.9%at a reaction temperature of 800℃.Additionally,the influences of reaction temperature,steam-to-carbon ratio(S/C),and liquid hourly space velocity(LHSV)were also examined.Moreover,during the 40-h continuous SR process of LA,the 15Ni/NiAl_(2)O_(4)catalyst maintained its outstanding catalytic activity.This study provides an encouraging route for upgrading biomass-derived LA into eco-friendly and high-value fuels,thereby advancing the sustainability of the biomass refining process.

Comparative study of microwave-assisted versus conventional heated reactions of biomass conversion into levulinic acid over hierarchical Mn_(3)O_(4)/ZSM-5 zeolite catalysts

Conversion of delignified cellulose from rice husk biomass,and model compounds of cellobiose and glucose to levulinic acid(LA)over hierarchical Mn_(3)O_(4)/ZSM-5 catalyst was carried out using a household microwave method,and then compared to the established conventional thermos-reaction method.The hierarchical ZSM-5 was prepared using a double template method,aiming for micro and mesoporous systems developed in the structure.The as-prepared ZSM-5 were modified with Mn3O4 through incipient wetness impregnation with Mn2+solution followed by calcination at 550℃.The catalysts were characterized using various techniques such as powder XRD,SEM,BET,AAS,and FT-IR which indicated the hierarchical structure of MFI zeolite(Si/Al of 30-34)with Mn loading of 2.14 wt%.The conversion products were analyzed using HPLC,1H NMR,and 13C NMR instruments.The microwave-assisted reaction using 600 W for 180 s using delignified cellulose,cellobiose,and glucose gave conversion of 37.27%,46.35%,and 54.29%,respectively which is close to the conversion given by the conventional reaction carried out at 130◦C for 4 h(36.75%,55.62%,and 60.9%,respectively).Interestingly,the LA yield from the microwave-assisted reaction(4.33%,6.12%,and 9.57%)is higher than the yield from the conventional reaction,which only produced 5.2%,4.88%,and 6.93%respectively.The microwaveassisted method is also shown to give less by-products compared to the thermochemical reaction.Therefore,it could be considered an alternative method for converting cellulose to LA.

Esterification of levulinic acid into n-butyl levulinate catalyzed by sulfonic acid-functionalized lignin-montmorillonite complex

In this study,sulfonic acid-functionalized lignin-montmorillonite complex(LMT-SO_(3)H)was pre-pared and employed as an efficient heterogeneous catalyst for the esterification of levulinic acid(LA)into n-butyl levulinate(BL).An intermediate pseudo-butyl levulinate(p-BL)was determined by distilled water treatment and nuclear magnetic resonance(NMR)analysis,and a possible mech-anism for the esterification of LA is proposed.The effects of various process parameters were studied and the results showed that the LMT-SO_(3)H catalyst had the excellent catalytic perfor-mance for esterification of the LA.Under optimum reaction conditions,the yield of BL was 99.3%and the conversion of LA was 99.8%.The LMT-SO_(3)H catalyst exhibited strong acidic sites and high stability even after seven cycles of usage.Furthermore,esterification of the LA with various alcohols over the LMT-SO_(3)H was further investigated.

Iridium-Catalyzed Reductive Amination of Levulinic Acid to Pyrrolidinones under H2 in Water

The synthesis of pyrrolidinones from reductive amination of levulinic acid （LA） with primary amines is reported.Pyrrolidinones have various applications such as surfactants,pharmaceutical intermediates,dispersants,and solvents.The half-sandwich Cp＊Ir complex （Cp＊ is 1,2,3,4,5-pentamethylcyclopenta-l,3-diene） coordinated by bipyridine ligand bearing both dimethylamino and ortho-hydroxyl groups showed high catalytic activity for the reductive amination of LA.A range of primary amines,such as aromatic and benzyl amines,were readily converted to corresponding pyrrolidinones in good yields.

Promotional effect of Mn doping on Ru/layered MCM-49 catalysts for the conversion of Levulinic acid to γ-Valerolactone

Selective hydrogenation of Levulinic acid(LA)toγ-Valerolactone(GVL)is an important reaction to produce high value-added chemicals and fuels but remains a big challenge.Herein we reported a Ru/zeolite catalyst with Mn promotion,which exhibited excellent catalytic performance(yield:98%)towards LA to GVL.The intrinsic activity(TOF)also increased obviously with the Mn addition.The particle size of Ru gradually decreased with the increase of Mn loading and a strong interaction between Ru and support was observed for the Ru-Mn/MCM-49 catalyst.The addition of Mn not only offered a good dispersion of Ru species on MCM-49,but also increased the L/B ratio of the catalyst,thereby contributing to the high GVL selectivity.High dispersed Ru sites were the intrinsic active sites of the catalyst verified by the in-situ experimental studies.The dissociation of the reactants was significantly enhanced,resulting in higher catalytic activity.

Different characteristics of 40 kinds of free amino acids and 5-amino levulinic acid between wines and sakes(Japanese rice wines)

Based on a systemic analysis for the globa1 burden of disease study from 1990 to 2016,the Global Burden of Diseases(GBD)2016 Alcohol Collaborators reported that alcohol use was a 1eading nisk factor for globa1 disease burden and caused substantial health loss.However,alcoholic dnink(wines and sakes)contains abundant nutrients,particularly fermentable amino acids denived from grapes and rice.Amino acid nutrition and metabolism is strongly associated with health and preventiom against various diseases.The purpose of this study was to elucidate 40 kinds of free amino acid(FAA)profles in wines and sakes.In addition,the present study also provided the contents of 5-aminolevulinic acid(5-AI A)involved in the vital functionality of mitochondria.FAAs were detected and analyzed by use of an automatic amino acid analyzer.Aromatic amino acid,branched chain amino acid and Fischer ratio were calculated for each beverage.Individua1 FAAs showed significant differences between wines and sakes.Sakes abundantly contained almost all FAAs whereas wines had just a lttle content in some FAAs.Sakse were rich in arginine,glycine,alanine,valine,glutamic acid and leucine,while wines were remarkably nich in proline(Pro).Wines showed increased FAA levels in 6 kinds of variables(4-hydroxyproline,3-methy1 histidine,B-alanine,a-aminobutyric acid,Pro and a.-aminoadipic acid).In functionally characteristic FAAs,both wines and sakes were considerably abundant in y aminobutynic acid and 5-AI A The total amount of aromatic amino acid and branched chain amino acid were markedly higher in sakes than in wines.These results revealed that there were the apparent different characteristics in FAA profiles between wines and sakes.This difference resulted from fermentation process in wines(single fermentation)and sakes(paralle1 double fermentation).Forty kinds of FAA profiles are more usefu1 in investigating characteristics of the taste of wines and sakes.In future,detailed FAA analysis has the potential to find functional nutrients such as 5-AI A,whereas other foods generally contain ittle amount of these FAAs.

Production of octyl levulinate biolubricant over modified H-ZSM-5:Optimization by response surface methodology

The present study highlighted the use of modified H-ZSM-5 （Meso-HZ-5） as heterogeneous catalyst for the synthesis of octyl levulinate biolubricant by catalytic esterification of biomass derived renewable levulinic acid （LA） with n-octanol. The process variables such as catalyst loading （X1）, n-octanol to LA molar ratio （X2） and reaction temperature （X3） were optimized through response surface methodology （RSM）, using Box-Behnken model. Analysis of variance was performed to determine the adequacy and significance of the quadratic model. The yield of octyl levulinate was obtained to be 99% at optimum process parameters. The developed quadratic model was found to be adequate and statistically accurate with correlation value （R2） of 0.9971 to predict the yield of octyl levulinate biolubricant. The study was also extended on the validation of theoretical and experimental data, including catalyst reusability.

Influence of Montmorillonite Nanocomposite on Tissue Levels of Lead and Blood Biochemical Parameters in Pigs Exposed to Lead

ABSTRACT： Eighteen （Duroc x Landrace x Yorkshire） castrated boars, 55 days of age and weig- hing approximately 19 kg, were used to investigate the effects of montmorillonite nanocomposite on tissue levels of lead as well as changes in blood biochemical parameters in pigs fed lead contaminated diets. The barrows were randomly assigned to one of three treat- ments （n = 6） including a control which were fed a basal diet based on corn and soybean meal. The re- maining two groups were fed the basal diet supple- mented with 10 mg/kg lead either with or without 0.5% montmorillonite nanocomposite for 50 days. Pigs treated with lead had significantly increased lev- els of lead in their tissues. Lead accumulated in all tis- sues of the body with the highest accumulation found in the hair. When montmorillonite nanocomposite was given along with lead, tissue concentrations of lead did not differ from the control. Fecal excretion of leadincreased significantly in lead-exposed pigs treated with montmorillonite nanocomposite. A progressive and appreciable accumulation of lead was seen in blood with a concomitant increase in zinc protopor- phyrin levels during the course of treatment. Howev- er, zinc protoporphyrin levels did not differ from the control when montmorillonite nanocomposite was ad- ministered along with lead. The activity of ^-amino le- vulinic acid dehydratase in blood was significantly in- creased in lead treated pigs compared with the con- trol. However, in pigs treated with lead and montmo- riltonite nanocomposite in combination, the activity of δ-amino levulinic acid dehydratase was similar to con- trol pigs. Our results indicate that montmorillonite nanocomposite treatment of pigs exposed to lead re- suited in reduced lead concentrations in body tissues. It appears that montmorillonite nanocomposite func- tions by increasing fecal excretion of lead.

Impact of Essential Micronutrient, Zn, on Growth and Chlorophyll Biosynthesis in Young <i>Zea mays</i>Seedlings

The present study analyses growth and chlorophyll biosynthesis in young maize seedlings in response to Zn supply over a wide range of concentrations. Supply of 0 - 5 mM ZnCl2 to 3 days old light grown maize seedlings led to gradually increased accumulation of Zn in the shoot tissue, while in the root tissue substantial increase was observed at/and above 0.1 mM ZnCl2. Zn supply significantly reduced the overall growth of maize seedlings mostly at 1 - 5 mM ZnCl2 exerting strong correlation and the observed effect was more substantial for root tissue. Amongst the biochemical parameters, increase in protein and proline content was more prominent in root tissue than the shoot, while RNA content was reduced in shoot tissue. Zn treatment to light grown seedlings significantly increased the chlorophyll, carotenoid content, while in dark grown seedlings it had marginal/no effect. Delta amino levulinic acid (ALA) content in both the regimes was increased at higher Zn concentrations. Also ALA synthesis was increased in both the regimes, but non significantly. Zn enhanced ALA dehydratase (ALAD) activity of light as well as dark grown seedlings being significant in former. The results demonstrate that the Zn accumulation and growth effect at higher Zn concentrations in maize depend upon the tissue with root as the target site and shoot growth are mainly influenced by ALA and subsequently ALAD in maize seedlings.