Kinetic characterization of arginase from Saccharomyces cerevisiae during alcoholic fermentation at different temperatures

The effect of plum extracts and antioxidants on reduction of ethyl carbamate in plum liqueur

Stone-fruit liqueurs contain high contents of the carcinogen ethyl carbamate (EC). In this study, we investigated the effect of plum fruit extract and single antioxidants present in plum fruit extracts on the reduction in the EC content during the macerating process in a plum liqueur model system and authentic plum liqueur. 30% ethanol model plum liqueur treated with 0.2% plum extract showed the lowest EC content with 55% reduction rate after the macerating process compared to the content in the control. Interestingly, neither 0.1% ascorbic acid nor 0.1% p-coumaric acid lowered the EC contents in the model liqueur, while they decreased the EC contents in authentic plum liqueur. This was possibly attributed to the synergistic effect of the plum fruit phenolics with the ascorbic acid and p-coumaric acid antioxidants. Thus, plum extracts can be applied to plum liqueurs to reduce the rate of EC formation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-024-01585-1.

Research progress on the application of different controlling strategies to minimizing ethyl carbamate in grape wine

Ethyl carbamate (EC) is a probable carcinogenic compound commonly found in fermented foods and alcoholic beverages and has been classified as a category 2A carcinogen by the International Agency for Research on Cancer (IARC). Alcoholic beverages are one of the main sources of EC intake by humans. Therefore, many countries have introduced a standard EC limit in alcoholic beverages. Wine is the second largest alcoholic beverage in the world after beer and is loved by consumers for its rich taste. However, different survey results showed that the detection rate of EC in wine was almost 100%, while the maximum content was as high as 100 μg/L, necessitating EC content regulation in wine. The existing methods for controlling the EC level in wine mainly include optimizing raw fermentation materials and processes, using genetically engineered strains, and enzymatic methods (urease or urethanase). This review focused on introducing and comparing the advantages, disadvantages, and applicability of methods for controlling EC, and proposes two possible new techniques, that is, changing the fermentation strain and exogenously adding phenolic compounds. In the future, it is hoped that the feasibility of this prospect will be verified by pilot-scale or large-scale application to provide new insight into the regulation of EC during wine production. The formation mechanism and influencing factors of EC in wine were also introduced and the analytical methods of EC were summarized.

A Minimally Invasive Approach for Preventing White Wine Protein Haze by Early Enzymatic Treatment

Protein stability in bottled white wine is an essential organoleptic property considered by consumers. In this paper, the effectiveness of an early enzymatic treatment was investigated by adding a food-grade microbial protease at two different stages of winemaking: (i) at cold settling, for a short-term and low temperature (10 °C) action prior to alcoholic fermentation (AF); (ii) at yeast inoculum, for a long-lasting and medium temperature (18 °C) action during AF. The results reveal that protease sufficiently preserved its catalytic activity at both operational conditions: 10 °C (during cold settling) and 18 °C (during AF). Furthermore, protease addition (dosage 50–150 μL/L) raised the alcoholic fermentation rate. The treatment at yeast inoculum (dosage 50 μL/L) had a remarkable effect in preventing haze formation, as revealed by its impact on protein instability and haze-active proteins. This minimally invasive, time and resource-saving enzymatic treatment, integrated into the winemaking process, could produce stable white wine without affecting color quality and phenol content.

Arginine depriving enzymes: applications as emerging therapeutics in cancer treatment

Cancer is the second leading cause of death globally. Chemotherapy and radiation therapy and other medications are employed to treat various types of cancer. However, each treatment has its own set of side effects, owing to its low specificity. As a result, there is an urgent need for newer therapeutics that do not disrupt healthy cells' normal functioning. Depriving nutrient or non/semi-essential amino acids to which cancerous cells are auxotrophic remains one such promising anticancer strategy. L-Arginine (Arg) is a semi-essential vital amino acid involved in versatile metabolic processes, signaling pathways, and cancer cell proliferation. Hence, the administration of Arg depriving enzymes (ADE) such as arginase, arginine decarboxylase (ADC), and arginine deiminase (ADI) could be effective in cancer therapy. The Arg auxotrophic cancerous cells like hepatocellular carcinoma, human colon cancer, leukemia, and breast cancer cells are sensitive to ADE treatment due to low expression of crucial enzymes argininosuccinate synthetase (ASS), argininosuccinate lyase (ASL), and ornithine transcarbamylase (OCT). These therapeutic enzyme treatments induce cell death through inducing autophagy, apoptosis, generation of oxidative species, i.e., oxidative stress, and arresting the progression and expansion of cancerous cells at certain cell cycle checkpoints. The enzymes are undergoing clinical trials and could be successfully exploited as potential anticancer agents in the future.

Expression, isolation, and identification of an ethanol-resistant ethyl carbamate-degrading amidase from Agrobacterium tumefaciens d3

Ethyl carbamate (EC), widely found in alcoholic beverages, has been revealed to be a probable carcinogen in humans. Urethanase (EC 3.5.1.75) is an effective enzyme for the degradation of EC; however, the previously identified urethanases exhibited insufficient acid and alcohol resistance. In this study, an enantioselective amidase (AmdA) screened from Agrobacterium tumefaciens d₃ exhibited urethanase activity with excellent alcohol resistance. AmdA was first overexpressed in Escherichia coli; however, the recombinant protein was primarily located in inclusion bodies, and thus, co-expression of molecular chaperones was used. The activity of AmdA increased 3.1 fold to 307 U/L, and the specific activity of urethanase with C-terminal His-tags reached 0.62 U/mg after purification through a Ni-NTA column. Subsequently, the enzymatic properties and kinetic constants of AmdA were investigated. The optimum temperature for AmdA was 55 °C, it showed the highest activity at pH 7.5, and the K_m was 0.964 mM. Moreover, after 1 h of heat treatment at 37 °C in a 5-20% (v/v) ethanol solution, the residual urethanase activity was higher than 91%, considerably more than that reported thus far.

Catalytic properties of lipoxygenase extracted from different varieties of Pisum sativum and Lens culinaris

Lipoxygenase (LOX, E.C. 1.13.11.12), among its various roles, catalyzes the degradation of polyunsaturated fatty acids and it is considered to be one of the main causes of undesirable off-flavor developments in legumes. The role of LOX in postharvest physiology is particularly significant in seeds with high values of lipoxygenase and linoleic acid levels. This research aimed to study the biochemical properties of the LOX extracted from green pea (Pisum sativum L. var. Léda, Zeusz, Zsuzsi), dry pea (Pisum sativum L. var. Hanka, Irina, Lutra), and lentil (Lens culinaris L., var. Pinklevi, Rézi, Castelluccio), using linoleic acid as a substrate. The raw extracts showed different catalytic properties, with dry pea (var. Irina) that expressed the highest LOX activity, while lentil (var. Pinklevi) expressed the lowest activity. To complete the biochemical characterization of the crude LOX extracts, their optimal pH and temperature were also examined. The highest value of lipoxygenase activity in the pH range 6-7 was measured in all legumes. The optimal temperature for all extracts fell within the range of 30-60°C given the nutritional importance of legumes. This study will serve as a basis for further detailed investigation of the legumes LOX activity and its roles in food products related to legumes. PRACTICAL APPLICATIONS: This study investigated the biochemical properties of lipoxygenase (LOX) extracted from different varieties of lentil and pea, the two important leguminous crops serving as the main protein source for the population of humans worldwide. The biochemical properties of LOX extracted from legumes showed large differences in terms of kinetic properties. The results of this study revealed that the use of lipoxygenase can be a suitable index for managing stabilization techniques of lentil and pea, in order to inhibit the lipid oxidation in grain legume without compromising its nutritional value.

An Overview of CRISPR-Based Technologies in Wine Yeasts to Improve Wine Flavor and Safety

Modern industrial winemaking is based on the use of specific starters of wine strains. Commercial wine strains present several advantages over natural isolates, and it is their use that guarantees the stability and reproducibility of industrial winemaking technologies. For the highly competitive wine market with new demands for improved wine quality and wine safety, it has become increasingly critical to develop new yeast strains. In the last decades, new possibilities arose for creating upgraded wine yeasts in the laboratory, resulting in the development of strains with better fermentation abilities, able to improve the sensory quality of wines and produce wines targeted to specific consumers, considering their health and nutrition requirements. However, only two genetically modified (GM) wine yeast strains are officially registered and approved for commercial use. Compared with traditional genetic engineering methods, CRISPR/Cas9 is described as efficient, versatile, cheap, easy-to-use, and able to target multiple sites. This genetic engineering technique has been applied to Saccharomyces cerevisiae since 2013. In this review, we aimed to overview the use of CRISPR/Cas9 editing technique in wine yeasts to combine develop phenotypes able to increase flavor compounds in wine without the development of off-flavors and aiding in the creation of “safer wines.”

Oxo-Free Hydrocarbon Oxidation by an Iron(III)-Isoporphyrin Complex

Metal-halides that perform proton coupled electron-transfer (PCET) oxidation are an important new class of high-valent oxidant. In investigating metal-dihalides, we reacted [Fe^III(Cl)(T(OMe)PP)] (1, T(OMe)PP = meso-tetra(4-methoxyphenyl)porphyrinyl) with (dichloroiodo)benzene. An Fe^III-meso-chloro-isoporphyrin complex [Fe^III(Cl)₂(T(OMe)PP-Cl)] (2) was obtained. 2 was characterized by electronic absorption, ¹H NMR, EPR, and X-ray absorption spectroscopies and mass spectrometry with support from computational analyses. 2 was reacted with a series of hydrocarbon substrates. The measured kinetic data exhibited a nonlinear behavior, whereby the oxidation followed a hydrogen-atom-transfer (HAT) PCET mechanism. The meso-chlorine atom was identified as the HAT agent. In one case, a halogenated product was identified by mass spectrometry. Our findings demonstrate that oxo-free hydrocarbon oxidation with heme systems is possible and show the potential for iron-dihalides in oxidative hydrocarbon halogenation.

Ethyl carbamate: An emerging food and environmental toxicant

Ethyl carbamate (EC), a chemical substance widely present in fermented food products and alcoholic beverages, has been classified as a Group 2A carcinogen by the International Agency for Research on Cancer (IARC). New evidence indicates that long-term exposure to EC may cause neurological disorders. Formation of EC in food and its metabolism have therefore been studied extensively and analytical methods for EC in various food matrices have been established. Due to the potential threat of EC to human health, mitigation strategies for EC in food products by physical, chemical, enzymatic, and genetic engineering methods have been developed. Natural products are suggested to provide protection against EC-induced toxicity through the modulation of oxidative stress. This review summarizes knowledge on the formation and metabolism of EC, detection of EC in food products, toxic effects of EC on various organs, and mitigation strategies including prevention of EC-induced tumorigenesis and genotoxicity by natural products.