Fatma Gassara

Bisphenol A degradation in water by ligninolytic enzymes

Many endocrine disruptor compounds, such as bisphenol A (BPA) are used today and released into the environment at low doses but they are barely degraded in wastewater treatment plants. One of the potential alternatives to effectively degrade endocrine disruptor compounds is based on the use of the oxidative action of extracellular fungal enzymes. The aim of this work is to study the ability of free and encapsulated enzymes (manganese peroxidase, lignin peroxidase and laccase) to degrade BPA. Higher degradation of BPA (90%) by ligninolytic enzymes encapsulated on polyacrylamide hydrogel and pectin after 8h was obtained. The degradation of BPA while using the free enzyme (26%) was lower than the value obtained with encapsulated enzymes. The presence of pectin in the formulation significantly (p>0.05) enhanced the activity of enzymes. Kinetics of BPA degradation showed an increase in Vm, while Km remained constant when enzymes were encapsulated. Hence, encapsulation protected the enzymes from non-competitive inhibition.

Improved xylanase production using apple pomace waste by Aspergillus niger in koji fermentation

Xylanase production by Aspergillus niger NRRL‐567 in solid‐state fermentation (koji fermentation) was optimized using 24 factorial design and response surface methodology. The evaluated variables were the initial moisture level and concentration of inducers [veratryl alcohol (VA), copper sulphate (CS), and lactose (LAC)], leading to the response of xylanase production. Initial moisture level and LAC were found to be the most significant variable for xylanase production (p<0.05). The highest xylanase production was observed with 3578.8 ± 65.3 IU/gds (gram dry substrate) under optimal conditions using initial moisture of 85% (v/w), pH 5.0 and inducers VA (2 mM/kg), LAC 2% (w/w), and CS (1.5 mM/kg) after 48 h of incubation time. Higher xylanase activity of 3952 ± 78.3 IU/gds was attained during scale‐up of the process in solid‐state tray fermentation under optimum conditions after 72 h of incubation time. The present study demonstrates that A. niger NRRL‐567 can efficiently be used to achieve xylanase production with an economical and environmental benefit in solid‐state tray fermentation. The developed process can be used to develop an effective process for commercially feasible bioproduction of xylanases for speciality applications, such as conversion of lignocellulosic biomass to biofuels and other value‐added products.

Spice use in food: Properties and benefits

ABSTRACT Spices are parts of plants that due to their properties are used as colorants, preservatives, or medicine. The uses of spices have been known since long time, and the interest in the potential of spices is remarkable due to the chemical compounds contained in spices, such as phenylpropanoids, terpenes, flavonoids, and anthocyanins. Spices, such as cumin (cuminaldehyde), clove (eugenol), and cinnamon (cinnamaldehyde) among others, are known and studied for their antimicrobial and antioxidant properties due to their main chemical compounds. These spices have the potential to be used as preservatives in many foods namely in processed meat to replace chemical preservatives. Main chemical compounds in spices also confer other properties providing a variety of applications to spices, such as insecticidal, medicines, colorants, and natural flavoring. Spices provide beneficial effects, such as antioxidant activity levels that are comparable to regular chemical antioxidants used so they can be used as a natural alternative to synthetic preservatives. In this review, the main characteristics of spices will be described as well as their chemical properties, different applications of these spices, and the advantages and disadvantages of their use.

C3–C4 Platform Chemicals Bioproduction Using Biomass

Platform chemicals composed of 3–4 carbons are group of chemicals that can be used as important precursors for making a variety of chemicals and materials, including solvents, fuels, polymers, pharmaceuticals, perfumes, and foods. At present, most of the commercial platform chemicals composed of 3–4 carbons are produced from petroleum-based products. However, fossil-derived resources are nonrenewable and their amount is increasingly depleting. Additionally, application of these materials has number of environmental concerns. To overcome these problems, increasing interest has focused on the development of sustainable technologies for producing these platform chemicals from renewable resources. Researchers have made significant progress in biological production using metabolic of platform chemicals using engineering-modified microorganisms. However, the production efficiency still needs to be improved for it to become economically viable. Further work on engineering these strains and exploring their tolerances and the use of low-cost renewable substrate like biomass may increase the yields of green platform chemicals to an industrial scale. In this review we focused on the current status of the bio-based production of major C3–C4 platform chemicals, by direct microbial bioconversion of renewable materials.

Biopolymers Synthesis and Application

Living organisms, namely, prokaryotes and eukaryotes, are able to synthesize a variety of polymers, such as nucleic acids, proteins, and other polyamides, polysaccharides, polyesters, polythioesters, polyanhydrides, polyisoprenoids, and lignin. Microorganisms provide a source of biopolymers and biopolysaccharides from renewable sources. Bacteria are capable of yielding biopolymers with properties comparable to plastics derived from petrochemicals, though more expensive. They have the additional advantage of being biodegradable. A wide range of microbial polysaccharides have been studied, and structure/function relationships for a number of these macromolecules have been determined. These biopolymers accomplish different essential and beneficial functions for the organisms. Among the biopolymers produced, many are used for various industrial applications. Currently, the biotechnological production of polymers has been mostly achieved by fermentation of microorganisms in stirred bioreactors. The biopolymers can be obtained as extracellular or intracellular compounds. Alternatively, biopolymers can also be produced by in vitro enzymatic processes. However, the largest amounts of biopolymers are still extracted from plant and animal sources. Biopolymers exhibit fascinating properties and play a major role in the food processing industry, e.g., modifying texture and other properties. Among the various biopolymers, polysaccharides and bioplastics are the most important in the food industry. This chapter will discuss the sources of polymers, their biosynthesis by different organisms, and their application in different fields.

Trends in Biological Degradation of Cyanobacteria and Toxins

Cyanobacteria are known as blue-green algae, blue-green bacteria, and Cyanophyta. They are present in both toxic and non-toxic forms and it is actually the toxic form which proliferates in the aquatic environment. There are principally two types of toxins (neurotoxin and hepatotoxin) which lead to adverse environmental and human health impacts. Thus, the cyanobacteria and their cyanotoxins must be eliminated from fresh waters (lakes, river) to avoid contamination of drinking water and prevent other environmental adversities. Several treatment methods, such as physical and chemical treatment comprising chlorination, ozonation, photooxidation, activated carbon, and biological treatment including utilization of pure microorganisms such as bacteria, virus, fungi, protozoa, among others have been studied to ensure higher elimination of cyanobacteria. The physico-chemical treatment is the most prevalent and faster than biological treatment. However, this treatment causes the lysis of cyanobacterial cells and releases cyanotoxins and other carcinogenic and mutagenic substances in to the medium. In this context, the biological treatment is an eco-friendly option for removal of cyanobacteria and their toxins present in fresh waters. This mini-review is an attempt to explore different aspects of the research in the field of removal of cyanobacteria. The review presents the ecological aspects of cyanobacteria, physical-chemical treatment methodologies in short, biological treatment of cyanobacteria and cyanotoxins in details as latter are potentially more toxic.