Cold-active microbial enzymes and their biotechnological applications

Microorganisms known as psychrophiles/psychrotrophs, which survive in cold climates, constitute majority of the biosphere on Earth. Their capability to produce cold-active enzymes along with other distinguishing characteristics allows them to survive in the cold environments. Due to the relative ease of large-scale production compared to enzymes from plants and animals, commercial uses of microbial enzyme are alluring. The ocean depths, polar, and alpine regions, which make up over 85% of the planet, are inhabited to cold ecosystems. Microbes living in these regions are important for their metabolic contribution to the ecosphere as well as for their enzymes, which may have potential industrial applications. Cold-adapted microorganisms are a possible source of cold-active enzymes that have high catalytic efficacy at low and moderate temperatures at which homologous mesophilic enzymes are not active. Cold-active enzymes can be used in a variety of biotechnological processes, including food processing, additives in the detergent and food industries, textile industry, waste-water treatment, biopulping, environmental bioremediation in cold climates, biotransformation, and molecular biology applications with great potential for energy savings. Genetically manipulated strains that are suitable for producing a particular cold-active enzyme would be crucial in a variety of industrial and biotechnological applications. The potential advantage of cold-adapted enzymes will probably lead to a greater annual market than for thermo-stable enzymes in the near future. This review includes latest updates on various microbial source of cold-active enzymes and their biotechnological applications.

Recent advances in polygalacturonase: Industrial applications and challenges

This review focuses on the applications of polygalacturonase (PG), one of the most commercially produced enzymes on the biocatalyst market, in the food, beverage, feed, textile, and paper industries. Most PGs are acidic mesophilic enzymes, as shown by a summary of their biochemical properties. However, the acidic PGs discovered to date are insufficiently effective for industrial applications. The sequence and structural characteristics of thermophilic PGs are analyzed based on the results of extensive discussions regarding the catalytic mechanism and structural characteristics of PGs with shared right-handed parallel β-helical structures. In addition, the molecular modification methods for obtaining thermostable PGs are systematically presented. Notably, the demand for alkaline heat-resistant PGs has increased significantly concurrent with the biomanufacturing industry development. Therefore, this review also provides a theoretical guideline for mining heat-resistant PG gene resources and modifying PG thermostability.

Production of cold-active pectinases by three novel Cladosporium species isolated from Egypt and application of the most active enzyme

Cladosporium parasphaerospermum, Cladosporium chlamydosporigenum, and Cladosporium compactisporum have all been discovered and characterized as new Cladosporium species. The three new species seemed to generate cold-active pectinases with high activity at pH 6.0 and 10 °C, pH 6.0 and 15 °C, and pH 5.0 and 15 °C, respectively, with the most active being C. parasphaerospermum pectinase. In submerged fermentation (SmF), C. parasphaerospermum produced the most cold-active pectinase with the highest activity and specific activity (28.84 U/mL and 3797 U/mg) after 8 days. C. parasphaerospermum cold-active pectinase was isolated using DEAE-Cellulose anion exchange resin and a Sephadex G 100 gel filtration column. The enzyme was purified 214.4-fold and 406.4-fold greater than the fermentation medium using DEAE-cellulose and Sephadex G 100, respectively. At pH 7.0 and 10 °C, pure pectinase had the highest activity (6684 U/mg), with Km and Vmax determined to be 26.625 mg/mL and 312.5 U/min, respectively. At 5 mM/mL, EDTA, MgCl2, and SDS inhibited the activity of pure pectinase by 99.21, 96.03, and 94.45%, respectively. The addition of 10 U/mL pure pectinase enhanced the yield of apple, orange, apricot, and peach juice by 17, 20, 13, and 24%, respectively, and improved the clarity and colour of orange juice by 194 and 339%, respectively. We can now add cold-active pectinase production to the long list of Cladosporium species that have been identified. We also report three new species that can be used in biotechnological solutions as active microbial pectinase producers. Although further research is needed, these distinct species might be used to decompose difficult and resistant pertinacious wastes as well as clear fruit juices.

A Comprehensive Insight into Fungal Enzymes: Structure, Classification, and Their Role in Mankind's Challenges

Enzymes have played a crucial role in mankind's challenges to use different types of biological systems for a diversity of applications. They are proteins that break down and convert complicated compounds to produce simple products. Fungal enzymes are compatible, efficient, and proper products for many uses in medicinal requests, industrial processing, bioremediation purposes, and agricultural applications. Fungal enzymes have appropriate stability to give manufactured products suitable shelf life, affordable cost, and approved demands. Fungal enzymes have been used from ancient times to today in many industries, including baking, brewing, cheese making, antibiotics production, and commodities manufacturing, such as linen and leather. Furthermore, they also are used in other fields such as paper production, detergent, the textile industry, and in drinks and food technology in products manufacturing ranging from tea and coffee to fruit juice and wine. Recently, fungi have been used for the production of more than 50% of the needed enzymes. Fungi can produce different types of enzymes extracellularly, which gives a great chance for producing in large amounts with low cost and easy viability in purified forms using simple purification methods. In the present review, a comprehensive trial has been advanced to elaborate on the different types and structures of fungal enzymes as well as the current status of the uses of fungal enzymes in various applications.

Pectinase secreted by psychrotolerant fungi: identification, molecular characterization and heterologous expression of a cold-active polygalacturonase from Tetracladium sp

Background

Pectinolytic enzymes, which are used in several industries, especially in the clarification process during wine and fruit juice production, represent approximately 10% of the global enzyme market. To prevent the proliferation of undesired microorganisms, to retain labile and volatile flavor compounds, and to save energy, the current trend is to perform this process at low temperatures. However, the commercially available pectinases are highly active at temperatures approximately 50 °C and poorly active at temperatures below 35 °C, which is the reason why there is a constant search for cold-active pectinases. In preliminary studies, pectinolytic activity was detected in cold-adapted yeasts and yeast-like microorganisms isolated from Antarctica. The aim of the present work was to characterize pectinases secreted by these microorganisms and to express the best candidate in Pichia pastoris.

Results

Degradation of pectin by extracellular protein extracellular extracts obtained from 12 yeast cultures were assayed in plates at 4 °C to 37 °C and pH from 5.4 to 7.0, obtaining positive results in samples obtained from Dioszegia sp., Phenoliferia glacialis and Tetracladium sp. An enzyme was purified from Tetracladium sp., analyzed by peptide mass fingerprinting and compared to genome and transcriptome data from the same microorganism. Thus, the encoding gene was identified corresponding to a polygalacturonase-encoding gene. The enzyme was expressed in Pichia pastoris, and the recombinant polygalacturonase displayed higher activity at 15 °C than a mesophilic counterpart.

Conclusions

Extracellular pectinase activity was found in three yeast and yeast-like microorganisms from which the highest activity was displayed by Tetracladium sp., and the enzyme was identified as a polygalacturonase. The recombinant polygalacturonase produced in P. pastoris showed high activity at 15 °C, representing an attractive candidate to be applied in clarification processes in the production of fermented beverages and fruit juices.

Electronic supplementary material

The online version of this article (10.1186/s12934-019-1092-2) contains supplementary material, which is available to authorized users.

Purification and Characterization of a Unique Pectin Lyase from Aspergillus giganteus Able to Release Unsaturated Monogalacturonate during Pectin Degradation

A pectin lyase, named PLIII, was purified to homogeneity from the culture filtrate of Aspergillus giganteus grown in submerged culture containing orange peel waste as carbon source. PLIII was able to digest apple pectin and citrus pectins with different degrees of methyl esterification. Interestingly, the PLIII activity was stimulated in the presence of some divalent cations including Pb²⁺ and was not significantly affected by Hg²⁺. Like other pectin lyases, PLIII is stimulated by but is not dependent on Ca²⁺. The main soluble product released during the degradation of pectic substances promoted by the PLIII is compatible with an unsaturated monogalacturonate. PLIII is a unique enzyme able to release unsaturated monogalacturonate as the only soluble product during the degradation of pectic substances; therefore, PLIII was classified as an exo-pectin lyase. To our knowledge, this is the first characterization of an exo-pectin lyase. The PLIII described in this work is potentially useful for ethanol production from pectin-rich biomass, besides other common applications for alkaline pectinases like preparation of textile fibers, coffee and tea fermentation, vegetable oil extraction, and the treatment of pulp in papermaking.

Efficient polygalacturonase production from agricultural and agro-industrial residues by solid-state culture of Aspergillus sojae under optimized conditions

Previously identified fungal pectinase producers of the species Aspergillus sojae were used for optimization of polygalacturonase production in solid-state fermentation applying Design of Experiment. The effects of media composition and several process parameters, like inoculum size, moisture level, incubation time and temperature on polygalacturonase activity were studied in screening and optimization investigations. Utilization of agricultural and agro-industrial by-products provided the establishment of a cost-efficient and sustainable process for enzyme production. Comparison of pectinase production by A. sojae ATCC 20235 and A. sojae CBS 100928 under optimized conditions yielded 6.9 times higher polygalacturonase activity by A. sojae ATCC 20235. Highest enzyme yield (909.5 ± 2.7 U/g) was obtained by A. sojae ATCC 20235 after 8 days at 30°C applying 30% sugar beet pulp as inducer substrate in combination with wheat bran as medium wetted at 160% with 0.2 M HCl. Furthermore, an overview of pectinolytic enzyme activities present in the extracts of both strains is provided. Protein profiles of both strains are given by SDS-PAGE electrophoresis, as well as zymograms for pectinolytic enzymes in comparison to commercial pectinase preparations.

Cold active pectinases: advancing the food industry to the next generation

Pectinase has been an integral part of commercial food processing, where it is used for degradation of pectin and facilitates different processing steps such as liquefaction, clarification and juice extraction. The industry currently uses pectinases from mesophilic or thermophilic microorganisms which are well established, but recently, there has been is a new trend in the food industry to adopt low-temperature processing. This trend is due to the potential economic and environmental advantages which the industry envisages. In order to achieve this change, an alternative for the existing pectinases, which are mostly mesophilic and temperature-dependent, must be identified, which can function efficiently at low temperatures. Psychrophilic pectinases derived from cold-adapted microorganisms, are known to function at low to freezing temperatures and may be an alternative to address the problem. Psychrophilic pectinases can be obtained from the vast microflora inhabiting various cold regions on earth such as oceans, Polar Regions, snow-covered mountains, and glaciers. This article is intended to study the advantages of cold active pectinases, its sources, and the current state of the research.

Aspergillus carbonarius polygalacturonases purified by integrated membrane process and affinity precipitation for apple juice production

Aspergillus carbonarius, when grown by submerged and solid-state fermentation, produces different molecular forms of polygalacturonase (PG; EC 3.2.1.15), among them a 42 kDa PG with a high specific activity of 7000 U/mg protein. When the enzymes were purified by integrated membrane process (IMP) and alginate affinity precipitation (AAP), the two processes concentrated different forms of the enzyme. The AAP process selectively purified and concentrated the high active PG whereas the IMP yielded different PGs and also amylase and protease. Evaluation of the AAP enzyme preparations for apple juice preparation under conditions usually employed commercially demonstrated that the high activity PG did not result in good juice clarity. With IMP processed enzymes, juice yields and clarity were similar to that obtained with commercial PG from A. niger.