Bioethanol has been identified as the mostly used biofuel worldwide since it significantly contributes to the reduction of crude oil consumption and environmental pollution. It can be produced from various types of feedstocks such as sucrose, starch, lignocellulosic and algal biomass through fermentation process by microorganisms. Compared to other types of microoganisms, yeasts especially Saccharomyces cerevisiae is the common microbes employed in ethanol production due to its high ethanol productivity, high ethanol tolerance and ability of fermenting wide range of sugars. However, there are some challenges in yeast fermentation which inhibit ethanol production such as high temperature, high ethanol concentration and the ability to ferment pentose sugars. Various types of yeast strains have been used in fermentation for ethanol production including hybrid, recombinant and wild-type yeasts. Yeasts can directly ferment simple sugars into ethanol while other type of feedstocks must be converted to fermentable sugars before it can be fermented to ethanol. The common processes involves in ethanol production are pretreatment, hydrolysis and fermentation. Production of bioethanol during fermentation depends on several factors such as temperature, sugar concentration, pH, fermentation time, agitation rate, and inoculum size. The efficiency and productivity of ethanol can be enhanced by immobilizing the yeast cells. This review highlights the different types of yeast strains, fermentation process, factors affecting bioethanol production and immobilization of yeasts for better bioethanol production.

https://cyberleninka.org/article/n/143136.pdf

Yeasts in sustainable bioethanol production: A review.

Since the discovery of the liquid-crystalline state of matter 125 years ago, this field has developed into a scientific area with many facets. This Review presents recent developments in the molecular design and self-assembly of liquid crystals. The focus is on new exciting soft-matter structures distinct from the usually observed nematic, smectic, and columnar phases. These new structures have enhanced complexity, including multicompartment and cellular structures, periodic and quasiperiodic arrays of spheres, and new emergent properties, such as ferroelctricity and spontaneous achiral symmetry-breaking. Comparisons are made with developments in related fields, such as self-assembled monolayers, multiblock copolymers, and nanoparticle arrays. Measures of structural complexity used herein are the size of the lattice, the number of distinct compartments, the dimensionality, and the logic depth of the resulting supramolecular structures.

Development of structural complexity by liquid-crystal self-assembly.

This review gives an updated picture of each class of phenolic compounds and their properties. The most common classification implies the subdivision of phenolics in two main groups: flavonoids (e.g., anthocyanins, flavanols, flavanones, flavonols, flavonones, and isoflavones) and non-flavonoids (e.g., phenolic acids, xanthones, stilbens, lignans, and tannins) polyphenols. The great interest in polyphenols is associated with their high potential application for food preservation and for therapeutic beneficial use. The relationship between polyphenol intake and human health has been exploited with special reference to cardiovascular diseases, hypertension, diabetes, metabolic syndrome, obesity, and cancer. The use of current existing databases of bioactive compounds including polyphenols is described as key tools for human health research.

/pdf/polyphenols-a-concise-overview-on-the-chemistry-occurrence-2evnm5d0qr.pdf

Polyphenols: A concise overview on the chemistry, occurrence, and human health

Yarrowia lipolytica has been developed as a production host for a large variety of biotechnological applications. Efficacy and safety studies have demonstrated the safe use of Yarrowia-derived products containing significant proportions of Yarrowia biomass (as for DuPont's eicosapentaenoic acid-rich oil) or with the yeast itself as the final product (as for British Petroleum's single-cell protein product). The natural occurrence of the species in food, particularly cheese, other dairy products and meat, is a further argument supporting its safety. The species causes rare opportunistic infections in severely immunocompromised or otherwise seriously ill people with other underlying diseases or conditions. The infections can be treated effectively by the use of regular antifungal drugs, and in some cases even disappeared spontaneously. Based on our assessment, we conclude that Y. lipolytica is a "safe-to-use" organism.

https://www.tandfonline.com/doi/pdf/10.3109/1040841X.2013.770386

Yarrowia lipolytica: safety assessment of an oleaginous yeast with a great industrial potential.

Use of Lawesson's reagent in organic syntheses.

Candida antarctica: lipase B (CALB) is the most widely studied enzyme, due to its high selectivity and catalytic activity in organic and polymer synthesis. To avoid organometallic catalysts in the synthesis of biodegradable polyesters, the enzymatic ring-opening polymerization of cyclic esters can be carried out with CALB as a biocatalyst. This paper reviews selected examples of the application of lipases in polymer chemistry covering the synthesis of cyclic ester monomers, linear and star oligomers, as well as well-defined high molar mass polymers with improved mechanical properties. It is shown that by the selection of appropriate conditions of temperature and solvent assortment, CALB effectively catalyzes the polymerization of large size lactones obtaining polyesters with Mn up to 80 kg mol−1. The chemical structure and main applications of described materials are also discussed. As the polymer recycling is an important topic from environmental point of view, we also described the potential applications of CALB in degradation process of aliphatic polyesters.

/pdf/candida-antarctica-lipase-b-as-catalyst-for-cyclic-esters-2vcxt2zyv4.pdf

Candida antarctica Lipase B as Catalyst for Cyclic Esters Synthesis, Their Polymerization and Degradation of Aliphatic Polyesters

Biocatalysts (enzymes and whole cells) play a crucial role in industrial processes allowing for efficient production of many important compounds, but their use has been limited because of the considerably unstable nature of enzymes. Immobilization often protects enzymes from environmental stresses such as pH, temperature, salts, solvents, inhibitors and poisons. Immobilization of cells containing specific enzymes has further advantages such as elimination of long and expensive procedures for enzymes separation and purification and it is vital to expand their application by enabling easy separation and purification of products from reaction mixtures and efficient recovery of catalyst. This review focuses on organic polymers (natural and synthetic) used as matrices for immobilization of microorganisms, mainly baker’s yeasts and potential application of immobilized cells in the chemical, pharmaceutical, biomedical and food industries.

/pdf/immobilization-of-yeast-on-polymeric-supports-4fsvf2wnb6.pdf

Immobilization of Yeast on Polymeric Supports

A series of 4‐decyloxy‐4′‐hydroxybiphenyl esters of α,ω‐alkanedicarboxylic acids containing two mesogenic units connected by a methylene spacer was synthesized. The mesogenic properties of the compounds were investigated by polarising optical microscopy, differential scanning calorimetry and X‐ray diffraction methods. A strong influence of the spacer length and its parity on the mesomorphic properties was found. A dramatic odd–even effect was observed for the clearing temperatures and entropies. Compounds with an even number of carbon atoms in the methylene spacer formed tilted smectic phases, whereas compounds with an odd number of carbon atoms in the spacer exhibited the B4 phase, characteristic of bent‐shaped molecules.

Odd–even effect in biphenyl‐based symmetrical dimers with methylene spacer – evidence of the B4 phase

Studies on the lipolytic activity of sonicated enzymes from Yarrowia lipolytica.

Lipases are enzymes that catalyse the hydrolysis of ester bonds of triglycerides ranging among biocatalysts of considerable physiological significance and industrial potential. Better understanding of the catalytic functions and achieving the possibility to control the biocatalysis process, in particular exploring some activators and inhibitors of lipases, seems to be crucial in the context of novel applications. The lipase activity is a function of interfacial composition: the enzyme can be there activated as well as denaturated or deactivated and the interface is an appropriate site for modulating lipolysis. Lipase inhibitor, interacts directly with the enzyme and inhibits lipase action. Alternatively, some compounds can postpone the lipolytic reaction via adsorption to the interphase or to the substrate molecules. The aim of this review is to summarise the current knowledge concerning human, animal and microbial lipase inhibitors, which were grouped into two categories: synthetic lipase inhibitors (including phosphonates, boronic acids and fats analogues) and natural compounds (including β-lactones and some botanical foodstuffs - plant extracts and plant metabolites, mainly polyphenols and saponins as well as peptides and some dietary fibers). The topics discussed include also inhibition issues from the viewpoint of obesity treatment. Among natural compounds able to inhibit lipase activity are β- lactones including orlistat. Orlistat is the only registered drug for obesity treatment in many countries and lipases are essential enzymes for lipid absorption - thus fat absorption or obesity can be controlled by lipase inhibition, especially pancreatic lipase which is responsible for the hydrolysis of over 80% of total dietary fats. Its effectiveness in obesity treatment was also described.

Ewa Białecka-Florjańczyk

Papers

Candida antarctica Lipase B as Catalyst for Cyclic Esters Synthesis, Their Polymerization and Degradation of Aliphatic Polyesters

Immobilization of Yeast on Polymeric Supports

Odd–even effect in biphenyl‐based symmetrical dimers with methylene spacer – evidence of the B4 phase

Studies on the lipolytic activity of sonicated enzymes from Yarrowia lipolytica.

Synthetic and Natural Lipase Inhibitors.