Mohamed Gargouri

• PhD
• Professor at University of Carthage

Bread is one of the most wasted food products worldwide owing to its short shelf life. However, bread residues present an inexpensive, abundant, and underutilized renewable substrate that is highly available for valorization into value-added products. In the present study, the feasibility of starch extraction from white bread waste is investigated....

The valorization of marine macroalgal biomass is among the most promising international programs focusing on the sustainable exploitation of marine environment. However, macroalgal biomass remains unexploited in Tunisia, even though it represents a highly abundant renewable biomass. The excessive proliferation of several algal species causes severe...

Virgin olive oil (VOO) quality has been essentially correlated to its minor component contents, mainly phenolic compounds. Nevertheless, the content and composition of these compounds could be affected by several factors, among them the composition and biochemical properties of olive fruits, principally olive endogenous enzyme activities. Otherwise...

Several plant species contain volatile compounds extracted as “essential oils” through different technologies. After essential oil extraction, the residual solid is a lignocellulosic solid waste. This work proposes the instant controlled pressure-drop (DIC) technology to autovaporize volatile compounds and modify the lignocellulosic matrix. Indeed,...

The development of alternatives to fossil fuels, such as bioethanol from lignocellulosic materials, is highly relevant due to the economic and environmental contexts. It is therefore important to study the potential of some raw materials specific to each region and to evaluate the different stages involved in the production of bioethanol. Four lign...

Food waste has been widely valorized in the past years in order to develop eco-friendly materials. Among others, bread waste is currently of increasing interest, as it is considered a huge global issue with serious environmental impacts and significant economic losses that have become even greater in the post-pandemic years due to an increase in ce...

The valorization of marine macroalgal biomass is among the most promising international programs focusing on the sustainable exploitation of marine environment. However, macro-algal biomass remains unexploited in Tunisia even though it represents a renewable and highly abundant biomass. This causes several environmental disorders due to the excessi...

Leather industry is making significant contributions to economic development. However, it is notably leading to a serious environmental pollution. Recently, the enzyme technology developments offer new opportunities for enzymatic application in leather making. In the present investigation, microbial lipases were studied and used in degreasing proce...

Quality of virgin olive oil (VOO) depends on phenolic molecules content, which depends on the biochemical characteristics of olive fruits, namely endogenous enzymes. In order to ascertain the influence of olive fruit ripening degree on the phenol content, enzyme activities in olive fruits, and the quality of the corresponding oils were studied duri...

Scombridae fish (tuna, bonito, and mackerel) have significant ecological and economic values. They are very appreciated by consumers worldwide for their high‐quality flesh and for their high nutritional value. However, consumption of Scombridae fish is potentially hazardous. Indeed, several cases of infections and toxicity linked to the consumption...

In Tunisia, despite the large annual production and the numerous citrus varieties under cultivation, citrus processing industries lack product diversity. Products based on dietary properties are a new trend aiming to develop innovative foods and to meet the requirements of the new customer class. In the present study, formulations of reduced sugar...

In this study, chemical composition and in vitro biological activities of artichoke by‐products (leaves, floral stems and bracts) issued from two Tunisian varieties were evaluated. Analysis was performed by means of high‐performance liquid chromatography with diode array detection coupled to electrospray ionisation mass spectrometric (LC/DAD/ESI‐MS...

Lignocellulosic biomass can be considered as one of the largest sources for the production of renewable biofuels (bioethanol). It involves an enzymatic treatment capable of ensuring the depolymerization of cellulose into fermentable sugars, followed by the production of ethanol by appropriate bacteriological fermentation. Proper destruction of the...

Since mass diffusion within plant is very weak because of its inappropriate natural structure, Retama raetam biomass was pretreated by thermo-mechanical process “Instant controlled pressure drop” DIC texturing technology prior to submitting it to enzymatic treatment. DIC technology involves subjecting lignocellulosic biomass to saturated steam pres...

In this study combined NaOH/H2SO4 pretreatment of lignocellulosic biomasses (palm fronds, eucalyptus chips, almond shells and Aleppo pine cones) were used to separate hemicellulose and lignin and improve enzymatic digestibility of cellulose. The recovered celluloses were hydrolyzed using Cellic C-Tec2 or Cellic H-Tech2. The optimal saccharification...

Fish processing industry generates a considerable amount of by‐products which represent an environmental problem. Only a small portion of these residues is used for the production of low marketable products. Therefore, industrially scalable processes yielding value‐added products would be highly desirable. Different to others studies, this work dea...

This paper focuses on valorization alternatives of several fractions of new feedstock as Juncus maritimus and Retama raetam through a specific laboratory-scale part of biorefinery way implying organosolv and chemical pretreatments as well as cellulose saccharification and alcoholic fermentation to obtain acceptable yields. After organosolv pretreat...

There is a rising demand for the development of new foods with dietary properties. Apricot kernel flour (AKF) could offer an exciting potential as protein source in cereal products. The aim of this work was to enrich bread with AKF. Partial substitutions of wheat flour (WF) with 4, 8, 12 and 24% AKF were carried out. Bread composition, hydration an...

One of the key challenges to both control foodstuff composition and detect chemical or biological contaminants in food is the availability of selective, sensitive, and reliable analytical methods. In this context, electrochemical biosensors are particularly attractive due to their low-cost, high sensitivity, and selectivity. They can be easily mini...

In this work, the transesterification reaction of isoamyl alcohol obtained from fusel oil and leading to the synthesis of isoamyl acetate was conducted simultaneously with in situ ethanol removal, which allows to shift the reaction equilibrium toward ester synthesis. The extracellular Aspergillus oryzae lipase was immobilized into calcium alginate....

Aspergillus oryzae, isolated from traditional Japanese food “Miso”, has efficiently catalyzed the direct esterification between acetic acid and cis-3-hexen-1-ol in organic solvent. The esterification between acids and alcohols having different chain lengths was initially investigated, observing a conversion decrement parallel to the increase of the...

The aim of the present work was firstly to study the impact of olive fruit ripening on olive endogenous enzyme activities and virgin olive oil (VOO) phenolic composition and secondly to determine the key enzymes contributing to VOO phenolic content, in order to define the optimum harvesting dates for Chétoui and Chemlali olives. An increase of β-gl...

The partial substitution of wheat flour (WF) by apricot kernel flour (AKF) in the range of 4–24 % was made. Physicochemical, hydration and pasting properties of WF–AKF blends were studied. The effect of AKF addition on the rheological and textural behaviours, respectively, of composite pastes and gels was also investigated. Flours blend exhibits hi...

In this study, a new fermentation medium combining a flocculated hemicellulosic wood hydrolysate (FHWH), rich in carbohydrates, obtained from a pulp and paper mill and an alfalfa juice, rich in nitrogen was used to produce butanol by Clostridium acetobutylicum ATCC 842. It was demonstrated that pH control enhances solvent production. The culture co...

The composition and biochemical characteristics of olive fruits, mainly olive enzymes system, are crucial in determining the final quality of virgin olive oil (VOO). Thus, olives endogenous olive enzyme activities were studied during Chétoui and Chemlali olive ripening. The compositional quality of the corresponding VOO was also studied. Peroxidase...

Several factors affect virgin olive oil (VOO) phenolic profile. The aim of this study was to monitor olive hydrolytic (β-glucosidase) and oxidative (POX and PPO) enzymes during olive ripening and storage and to determine their capacity to shape VOO phenolic profile. To this end, olives from the cultivars Chétoui and Arbequina were stored at 4 °C or...

The objective of this paper was to study the production and the mass transfer of geranyl acetate known for its interesting green odor properties. Lipase-catalyzed geranyl acetate production via transesterification reaction with ethyl acetate in organic solvent was investigated. The production was catalyzed by using immobilized lipase from Rhizomuco...

The oxidation of water-in-oil (W/O) emulsions was investigated, emphasizing the impact of compositional parameters. The emulsions had approximately the same average droplet size and did not show any physical destabilization throughout the study. In the absence of pro-oxidant ions in the aqueous phase, lipid oxidation of the W/O emulsions was modera...

The distinctive aroma of virgin olive oil is mainly attributed to its volatile profile including components responsible for positive attributes and others for sensory defects resulting from chemical oxidation and exogenous enzymes. For this reason, the evolution of volatile compounds from Chétoui and Arbequina virgin olive oils during olive ripenin...

The conversion of agricultural and agro-industrial wastes and residues into a spectrum of marketable products and energy is of great importance to the environment and to sustainable development. The objective of this study is to assess the feasibility of using alfalfa juice to substitute or supplement expensive nutrients in an acetone-butanol-ethan...

This work investigates the utilization of Eucalyptus chips and Aleppo pine cones as a feedstock for ethanol fuel production. Besides, we focus on the use of a new method for biomass pretreatment, namely instant controlled pressure drop (DIC). DIC treatment is a highly controlled process that combines steam pressure (up to 7 bar) with heat (up to 17...

A new experimental device was developed, based on the measurement of the heat flux dissipated during chemical reactions. The technique was exploited for real time monitoring of lipid oxidation in plant oils. The thermopiles were used in adiabatic configuration in order to measure the entire heat flux and improve sensitivity. Measurements were opera...

Herein, carboxypeptidase Y (CPY) and thermolysin (TLN) were compared as sensing elements to develop an original biosensor for the direct detection of ochratoxin A (OTA) in olive oil. Electrochemical detection of OTA was performed using biosensors containing either CPY or TLN immobilized through glutaraldehyde vapor cross-linking onto gold interdigi...

In this work, we propose a new technology for the pretreatment and the conversion of Retama raetam biomass into oligosaccharides and glucose based on Instant Controlled Pressure Drop (DIC). DIC technology is a thermo-mechanical method based on short-time/high-temperature and pressure pretreatment that avoids the thermal degradation of sugars. The m...

Juncus maritimus contains (41.5 ± 0.3)% cellulose and (31.34 ± 0.2)% hemicellulose on dry solid (DS) basis and has the potential to serve as a low cost feedstock for ethanol production. Dilute acid or freezing/thawing pretreatments and enzymatic saccharification were evaluated for conversion of halophyte plant from J. maritimus cellulose and hemice...

The feasibility of using hardwood hemicellulosic pre-hydrolysate recovered from a dissolving pulping process for Acetone-Butanol-Ethanol (ABE) fermentation has been investigated. Dilutions and detoxification methods based on flocculation and nanofiltration were tested to determine the inhibitory concentration of phenolic compounds and to evaluate t...

The ability of olive endogenous enzymes β-glucosidase, polyphenol oxidase (PPO) and peroxidase (POX), to determine the phenolic profile of virgin olive oil was investigated. Olives used for oil production were stored for one month at 20 °C and 4 °C and their phenolic content and enzymatic activities were compared to those of ripening olive fruits....

ABSTRACT: This monograph is a critical review of the biological activities that occur during virgin olive oil extraction process. Strategic choices of plant engineering systems and of processing technologies should be made to condition the enzymatic activities, in order to modulate the nutritional and the sensory quality of the product towards the...

In this work, new halophyte plant biomass is proposed as raw material for bioenergy production. The bioconversion process of lignocellulosic materials into ethanol needs a pretreatment before enzymatic hydrolysis of vegetal material to increase the yield of fermentable sugars. Various mechanical and chemical pre-treatment processes were investigate...

A new and simple method has been developed to allow the direct determination of pesticides in samples of vegetable oils via pH transduction. It is based on the inhibitory effect of the pesticides on the enzyme acetylcholinesterase (AChE). The strategy involves the use of a biphasic system composed of an organic phase (the oil) containing the pestic...

The results described in the present work concern the study of changes in gamma ray irradiated olive fruit (Tunisian variety: "Chemlali") quality along the storage time processing and the quality of olive oil issued. The study focused on the changes related to microbiological and physico-chemical properties, aswell as pectinase activities in olives...

In this work, a new method for determination of olive oil acidity is proposed. The method is based on the measurement of polyunsaturated free fatty acids reacting with lipoxygenase. Hydroperoxy-fatty acids enzymatically formed were easily determined by UV spectrophotometry at 234 nm. The proposed method is successfully applied to the determination...

The volatile profile of fourteen commercial virgin olive oils (VOOs) produced by Tunisian and Italian olive cultivars from different geographical areas and collected from local markets and farms was evaluated by means of headspace-solid phase microextraction and gas chromatography-mass spectrometry analysis. All the samples were also analyzed by a...

The volatile compounds responsible for the pleasant aroma of virgin olive oil are mainly derived from products of the lipoxygenase pathway. Lipoxygenase activity was assessed in olive pulp extracts. An optimization of its extraction by a 2 experimental design was performed. Four parameters considered as influencing the extraction were optimised usi...

A new, simple, and original method is described for specific measurement of polyunsaturated fatty acid content in olive oil. This analytical system uses coupled enzymes, lipase and lipoxygenase. The system consists of lipase-catalyzed hydrolysis of triacylglycerol and subsequent lipoxygenation of liberated polyunsaturated fatty acids. The hydropero...

Hydroperoxide-lyase is a suitable enzyme for the biocatalytic production of six-carbon aldehydes which are responsible for the “green notes” in many fruits and vegetables. The hydroperoxide-lyase isolated from olive leaves is used in this work. The effects of pH, temperature, and substrate and enzyme concentrations on hexenals generation were optim...

The effects of selected lyoprotecting excipients and chemical additives on the specific activity and the thermal stability of the hydroperoxide lyase (HPL) enzymatic extract from mint leaves were investigated. The addition of KCl (5%, w/w) and dextran (2.5%, w/w) to the enzymatic extract, prior to lyophilization, increased the HPL specific activity...

The production of lignin peroxidase (LiP), manganese peroxidase (MnP) and lipases by Geotrichum candidum were performed in order to control the decolourisation and biodegradation of olive mill wastewater (OMW). Optimisation of different factors showed that dilution, carbon and ammonium concentrations significantly affected decolourisation and activ...

Application of differential scanning calorimetry (DSC) to discriminate among extra virgin olive oils on the basis of cultivar–environment interaction was preliminary evaluated on Tunisian samples from two varieties (Chetoui and Chemlali) and different geographical origin relating thermal properties obtained by cooling and heating thermograms to che...

A novel biosensor assay format for aflatoxin based on acetylcholinesterase (AChE) inhibition by aflatoxin B(1) (AFB(1)) is proposed. The AChE was present in solution and an amperometric choline oxidase biosensor was used for monitoring its residual activity. To create the biosensor, the choline oxidase was immobilized by cross-linking onto screen-p...

The effect of γ-ray irradiation on alcohol-dehydrogenase activity of yeast was investigated. The results suggested that low doses of γ-ray (10 and 20 Gy) significantly increased the enzyme activity. This work also describes the impact of irradiation on immobilization efficiency of biocatalyst entrapped on to alginate gel beads. When yeast irradiate...

Lipoxygenase pathway: valorization of plant oils and aroma biosynthesis. This article is a review on the lipoxygenase pathway in plants, and its application in aroma compound synthesis from plant oils. Raw material used by this pathway is plant oils rich in poly-unsaturated fatty acids. Then, lipase-catalyzed hydrolysis followed by lipoxygenation,...

This article is a review on the lipoxygenase pathway in plants, and its application in aroma compound synthesis from plant oils. Raw material used by this pathway is plant oils rich in poly-unsaturated fatty acids. Then, lipase-catalyzed hydrolysis followed by lipoxygenation, hydroperoxyde-lyase and alcohol-dehydrogenase act successively producing...

The aim of the present work is to improve the extraction of an aromatic compound, 2E-hexenal, from a continuous liquid-gas reactor. Having an improved process to recover hexenal could be of interest to obtain this chemical if produced by any biotechnological process. The experimental program proposed on the basis of a full 23 factorial design demon...

Lipase activity against triacylglycerols has been measured using an amperometric enzyme biosensor based on glycerol dehydrogenase/NADH oxidase. A Prussian Blue modified screen-printed electrode was selected as substrate for the two immobilised-enzyme systems due to their higher operative stability reported in previous works. Various parameters such...

Based on its aromatic potential, Geotrichum candidum isolated from olive vegetation water was tested for the production of volatile compounds. When G. candidum was cultivated on media with glucose as the carbon source, flavor volatile compounds were produced and accumulated in the broth. Fruity flavoring compounds (pineapple-like) such as esters an...

β-Xylosidase and endo-xylanases form a part of an enzyme battery used by phytopathogenic fungifor the degradation of the cell walls. An enzyme preparation from Sclerotinia sclerotiorum was applied in the synthesis of biosurfactants such as hexyl-β-xyloside and hexyl-β-xylobioside from xylan and hexanol. Also, in order to characterize the enzyme act...

In a two-enzyme system, successive action of hydroperoxide lyase from mint and yeast alcohol-dehydrogenase catalyses the conversion of hydroperoxy linolenic acid to hexenol. Kinetic behaviour was investigated separately for each enzyme: a lumped model based on the Michaelis-Menten approach shows the fate of the reactants in the system.

The main objective of this work was to improve the selective synthesis of a volatile compound: aldehyde or alcohol using a coupled-enzyme system. A novel method of synthesis of C6-aldehyde or alcohol was carried out in the presence of hydroperoxide lyase (HPLS) activity coupled to alcohol dehydrogenase (ADH) activity. After cleavage of the initial...

A new method for lipase activity determination is described, in which liberation of fatty acids by lipase-catalyzed hydrolysis is coupled to lipoxygenation. The second reaction forms hydroperoxy-fatty acids containing a conjugated double bond that are detected at 234 nm. The method is sensitive, cheap and easy to use when compared to a titration me...

The extraction of 13-hydroperoxide-lyase activity from mint leaves as well as its use for C6-aldehyde production was studied in this work. The enzyme cleaves 13(S)-hydroperoxy-C18 fatty acids into C6-aldehyde and C12-oxo-acid. Two mint species were tested: Mentha veridis and Mentha pulegium. The headspace injection method coupled to gas chromatogra...

Production of β-glycosidases: β-xylosidase and β-glucosidase by the fungus Sclerotinia sclerotiorum was optimized in the presence of different carbon sources. Immobilization supports with different physico-chemical characteristics were evaluated for use in continuous reactors. Immobilization and activity yields were calculated. Among the adsorption...

The filamentous fungus Sclerotinia sclerotiorum, grown on a xylose medium, was found to excrete one β-glucosidase (β-glu x). The enzyme was purified to apparent homogeneity by ammonium sulfate precipitation, gel filtration, anion-exchange chromatography, and high-performance liquid chromatography (HPLC) gel filtration chromatography. Its molecular...

The filamentous fungus Sclerotinia sclerotiorum prudces ß-glucosidases in liquid culture with a variety of carbon sources, including cellulose (filter paper), xylan, barley straw, oat meal, and xylose. Analysis by native polyacrylamide gel electrophoresis (PAGE) followed by an activity staining with the specific chromogenic substrate, 5-bromo 4-chl...

The unsaturations and groups bound to the ring and to the lateral chain of lactones give a large diversity in this class of molecules. In this work we produced enzymatically a macrolactone in organic media. The substrate used was a hydroxy-fatty acid: (+)-coriolic acid and the enzymes tested were free or immobilized microbial lipases. The immobiliz...

A two-enzyme system involving a lipase from a Pseudomonassp. and an extract of potato tubers containing lipoxygenase was used to convert triacylglycerols to 9-hydroperoxy fatty acids. Highest yields (up to 25%) were obtained with 1 to 20 g l–1 trilinolein as substrate after 5 h under O2 at pH 6 and 25 C. The product structure was confirmed by 1H NM...

The penthylene-diammonium tetrachloromercurate (II) salt is triclinic centrosymmetric with the following unit cell dimensions: a= 7.7672(4)Å, b= 7.9754(6)Å, c= 10.9471(6)Å, α= 98.915(2)o, β= 109.363(2)o and γ= 91.463(2)o with Z= 2. The structure consists of disordered penthylene-diammonium chains sandwiched between HgCl6 octahedral layers. The chlo...

The penthylene-diammonium tetrachloromercurate (II) salt is triclinic centrosymmetric with the following unit cell dimensions: , , , α= 98.915(2)o, β= 109.363(2)o and γ= 91.463(2)o with Z= 2. The structure consists of disordered penthylene-diammonium chains sandwiched between HgCl6 octahedral layers. The chloromercurate sheet is packed as a result...

Soybean lipoxygenase-1 (EC 1.13.11.12) reaction with linoleic acid as substrate was used to study the biocatalysis in a biphasic system when the reactants have surface-active properties. The poorly water-soluble substrate was initially dissolved in an apolar solvent (octane). The hydroperoxide produced was water soluble and remained in the aqueous...

Nonenal synthesis from 9(S)-hydroperoxy-linoleic acid by hydroperoxide-lyase-catalysed cleavage was followed by a precise headspace analysis with GC-MS. Enzyme activity was extracted from plant leaves and fruits. 3Z-nonenal was the main product and a small amount of 2E-isomer was detected since the reaction-analysis procedure used avoided supplemen...

The bioconversion of polyunsaturated fatty acid triacylglycerols to hydroperoxides by the bienzymatic system consisting of lipase (EC 3.1.1.3)/lipoxygenase (EC 1.13.11.12) was investigated in a compartmentalized medium (octane/buffer pH 9, ). The presence of an organic phase (octane) in the system allowed high solubility of acylglycerols and a well...

Chemoenzymatic conversion of trilinolein to (+)-coriolic acid was investigated in this work. Lipase-catalyzed hydrolysis of trilinolein and lipoxygenation of liberated linoleic acid were coupled in a two-phase medium that consisted of a pH 9 borate buffer and a water-immiscible organic solvent (octane). High concentrations of trilinolein could be d...

Analysis of the kinetic behaviour of a two-enzyme-system carrying out two consecutive reactions was investigated in macroheterogeneous biphasic media (octane/buffer pH 9.6, v/v = 1:1). The lipase-catalysed hydrolysis of trilinolein and the subsequent lipoxygenation of the liberated linoleic acid, were coupled in a modified Lewis cell with a well-de...