The novel non-glycosylated invertase from Candida utilis (the properties and the conditions of production and purification)

The Influence of Yarrowia lipolytica Glycosylation on the Biochemical Properties and Oligomerization of Heterologous Invertase

Invertases are important enzymes used in the food industry. Despite many studies on the invertase-encoding SUC2 gene expression in the industrial yeast Yarrowia lipolytica, no biochemical characteristics of this enzyme expressed as heterologous protein have been provided. Here, two isoforms of extracellular invertase produced by Y. lipolytica were detected using ion-exchange chromatography. Specific activities of 226.45 and 432.66 U/mg for the first and second isoform, respectively, were determined. Basic characteristics of this enzyme were similar to the one isolated from Saccharomyces cerevisiae (optimum pH and temperature, metal ions inhibition, substrate specificity and fructooligosaccharides (FOS) biosynthesis). The apparent differences were higher KM for sucrose (67 mM) and lower molecular mass (66 kDa) resulting from lower N-glycosylation level (9.1% of mass). The N-glycan structures determined by MALDI-TOF and HPLC represented high mannose structures, though with much shorter chains than hypermannosylated glycans from S. cerevisiae. Furthermore, galactose was detected as the modifying sugar in the glycan structures of invertase expressed in Y. lipolytica. N-glycans did not affect invertase activity but were important for its oligomerization. The expressed enzyme aggregated into dimers, tetramers, hexamers, and octamers, as well as structures of higher molecular mass, which might be decamers, which have not been described so far in the literature.

Sucrose Hydrolysis in a Continuous Packed-Bed Reactor with Auto-immobilise Aspergillus niger Biocatalyst Obtained by Solid-State Fermentation

Invertase from Aspergillus niger C28B25 was produced by solid-state fermentation (SSF). Fermented solids were used directly as a biocatalyst for batch and continuous hydrolysis of sucrose in a packed-bed reactor under different operational conditions with various temperatures, sucrose concentrations, and feed flow rates. The SSF allowed obtaining a biocatalyst with an invertase activity of 82.2 U/g db. The biocatalyst maintained its activity in the range of 40 to 70 °C for at least 70 h of continuous operation. In a 20-mL packed bed reactor, the highest hydrolysis rate (12.3 g/g db h) was obtained at 40 °C with 2 M sucrose. Continuous hydrolysis in 20-mL and 200-mL reactors at 60 °C led to sucrose hydrolysis above 60% (8.5 residence times) and above 55% (4.5 residence times), respectively. The auto-immobilised biocatalyst produced by SSF without recovery, purification, and immobilisation stages offers an economical alternative for developing accessible biocatalysts that can be applied in batch or continuous sucrose hydrolysis processes. This study shows the potential of biocatalyst production by SSF for other enzymatic systems.

Yeast RNA exosome activity is necessary for maintaining cell wall stability through proper protein glycosylation

Nuclear RNA exosome is the main 3'→5' RNA degradation and processing complex in eukaryotic cells and its dysregulation therefore impacts gene expression and viability. In this work we show that RNA exosome activity is necessary for maintaining cell wall stability in yeast Saccharomyces cerevisiae. While the essential RNA exosome catalytic subunit Dis3 provides exoribonuclease catalytic activity, the second catalytic subunit Rrp6 has a noncatalytic role in this process. RNA exosome cofactors Rrp47 and Air1/2 are also involved. RNA exosome mutants undergo osmoremedial cell lysis at high temperature or at physiological temperature upon treatment with cell wall stressors. Finally, we show that a defect in protein glycosylation is a major reason for cell wall instability of RNA exosome mutants. Genes encoding enzymes that act in the early steps of the protein glycosylation pathway are down-regulated at high temperature in cells lacking Rrp6 protein or Dis3 exoribonuclease activity and overexpression of the essential enzyme Psa1, that catalyzes synthesis of the mannosylation precursor, suppresses temperature sensitivity and aberrant morphology of these cells. Furthermore, this defect is connected to a temperature-dependent increase in accumulation of noncoding RNAs transcribed from loci of relevant glycosylation-related genes.

Expanding the Knowledge on the Skillful Yeast Cyberlindnera jadinii

Cyberlindnera jadinii is widely used as a source of single-cell protein and is known for its ability to synthesize a great variety of valuable compounds for the food and pharmaceutical industries. Its capacity to produce compounds such as food additives, supplements, and organic acids, among other fine chemicals, has turned it into an attractive microorganism in the biotechnology field. In this review, we performed a robust phylogenetic analysis using the core proteome of C. jadinii and other fungal species, from Asco- to Basidiomycota, to elucidate the evolutionary roots of this species. In addition, we report the evolution of this species nomenclature over-time and the existence of a teleomorph (C. jadinii) and anamorph state (Candida utilis) and summarize the current nomenclature of most common strains. Finally, we highlight relevant traits of its physiology, the solute membrane transporters so far characterized, as well as the molecular tools currently available for its genomic manipulation. The emerging applications of this yeast reinforce its potential in the white biotechnology sector. Nonetheless, it is necessary to expand the knowledge on its metabolism, regulatory networks, and transport mechanisms, as well as to develop more robust genetic manipulation systems and synthetic biology tools to promote the full exploitation of C. jadinii.

Established and Upcoming Yeast Expression Systems

Yeast was the first microorganism used by mankind for biotransformation of feedstock that laid the foundations of industrial biotechnology. Long historical use, vast amount of data, and experience paved the way for Saccharomyces cerevisiae as a first yeast cell factory, and still it is an important expression platform as being the production host for several large volume products. Continuing special needs of each targeted product and different requirements of bioprocess operations have led to identification of different yeast expression systems. Modern bioprocess engineering and advances in omics technology, i.e., genomics, transcriptomics, proteomics, secretomics, and interactomics, allow the design of novel genetic tools with fine-tuned characteristics to be used for research and industrial applications. This chapter focuses on established and upcoming yeast expression platforms that have exceptional characteristics, such as the ability to utilize a broad range of carbon sources or remarkable resistance to various stress conditions. Besides the conventional yeast S. cerevisiae, established yeast expression systems including the methylotrophic yeasts Pichia pastoris and Hansenula polymorpha, the dimorphic yeasts Arxula adeninivorans and Yarrowia lipolytica, the lactose-utilizing yeast Kluyveromyces lactis, the fission yeast Schizosaccharomyces pombe, and upcoming yeast platforms, namely, Kluyveromyces marxianus, Candida utilis, and Zygosaccharomyces bailii, are compiled with special emphasis on their genetic toolbox for recombinant protein production.

Biochemical and Thermodynamical Characterization of Glucose Oxidase, Invertase, and Alkaline Phosphatase Secreted by Antarctic Yeasts

The use of enzymes in diverse industries has increased substantially over past decades, creating a well-established and growing global market. Currently, the use of enzymes that work better at ambient or lower temperatures in order to decrease the temperatures of production processes is desirable. There is thus a continuous search for enzymes in cold environments, especially from microbial sources, with amylases, proteases, lipases and, cellulases being the most studied. Other enzymes, such as glucose oxidase (GOD), invertase (Inv), and alkaline phosphatase (ALP), also have a high potential for application, but have been much less studied in microorganisms living in cold-environments. In this work, secretion of these three enzymes by Antarctic yeast species was analyzed, and five, three, and five species were found to produce extracellular GOD, Inv, and ALP, respectively. The major producers of GOD, Inv, and ALP were Goffeauzyma gastrica, Wickerhamomyces anomalus, and Dioszegia sp., respectively, from which the enzymes were purified and characterized. Contrary to what was expected, the highest GOD and Inv activities were found at 64°C and 60°C, respectively, and at 47°C for ALP. However, the three enzymes maintained a significant percentage of activity at lower temperatures, especially ALP that kept a 67 and 43% of activity at 10°C and 4°C, respectively.

Characterization of a novel low-temperature-active, alkaline and sucrose-tolerant invertase

A glycoside hydrolase family 32 invertase from Bacillus sp. HJ14 was expressed in Escherichia coli. The purified recombinant enzyme (rInvHJ14) showed typical biochemical properties of low-temperature-active and alkaline enzymes: (i) rInvHJ14 was active and stable in the range of pH 7.0–9.5 with an apparent pH optimum of 8.0; (ii) rInvHJ14 was most active but not stable at 30–32.5 °C, with 19.7, 48.2 and 82.1% of its maximum activity when assayed at 0, 10 and 20 °C, respectively, and the E_a, ΔG^* (30 °C), K_m (30 °C) and k_cat (30 °C) values for hydrolysis of sucrose by rInvHJ14 was 47.6 kJ mol⁻¹, 57.6 kJ mol⁻¹, 62.9 mM and 746.2 s⁻¹, respectively. The enzyme also showed strong sucrose tolerance. rInvHJ14 preserved approximately 50% of its highest activity in the presence of 2045.0 mM sucrose. Furthermore, potential factors for low-temperature-active and alkaline adaptations of rInvHJ14 were presumed. Compared with more thermostable homologs, rInvHJ14 has a higher frequency of glycine residues and a longer loop but a lower frequency of proline residues (especially in a loop) in the catalytic domain. The catalytic pockets of acid invertases were almost negatively charged while that of alkaline rInvHJ14 was mostly positively charged.

Transforming the blood glucose meter into a general healthcare meter for in vitro diagnostics in mobile health

Recent advances in mobile network and smartphones have provided an enormous opportunity for transforming in vitro diagnostics (IVD) from central labs to home or other points of care (POC). A major challenge to achieving the goal is a long time and high costs associated with developing POC IVD devices in mobile Health (mHealth). Instead of developing a new POC device for every new IVD target, we and others are taking advantage of decades of research, development, engineering and continuous improvement of the blood glucose meter (BGM), including those already integrated with smartphones, and transforming the BGM into a general healthcare meter for POC IVDs of a wide range of biomarkers, therapeutic drugs and other analytical targets. In this review, we summarize methods to transduce and amplify selective binding of targets by antibodies, DNA/RNA aptamers, DNAzyme/ribozymes and protein enzymes into signals such as glucose or NADH that can be measured by commercially available BGM, making it possible to adapt many clinical assays performed in central labs, such as immunoassays, aptamer/DNAzyme assays, molecular diagnostic assays, and enzymatic activity assays onto BGM platform for quantification of non-glucose targets for a wide variety of IVDs in mHealth.

Transfructosylation reaction in cured tobacco leaf (Nicotiana tabacum)

Tobacco plant was known to be a non-fructan-storing plant. However, we demonstrated that fructo-oligosaccharides (FOSs) were formed in cured tobacco leaf on adding sucrose to the leaf in our previous report (Nagai et al., J. Agric. Food Chem., 60, 6606-6612, 2012). Also, it was expected from the results obtained in previous study that FOSs were generated by enzymatic reaction in cured tobacco leaf. The purpose of this study is to confirm and understand the mechanisms of above-mentioned FOSs formation. Thus, we tried to purify the enzymes related to the production of FOSs. The enzymes were extracted from pulverized cured tobacco leaf (burley type leaf), and were purified by charcoal treatment, ultrafiltration, and several chromatography techniques. As a result, one of the enzymes was purified up to 414-fold. It was revealed that this enzyme was acid invertase exhibiting maximum transfructosylation activity at pH 6.0, 60 °C. In addition, general properties of this enzyme were also investigated. The enzyme purified in this study enhanced the ratio of FOSs formation under the condition of high concentrated sucrose. From these results, it was suggested that this enzyme participated in the formation of FOSs in tobacco leaf after curing.

Stimulation of extracellular invertase production from spent yeast when sugarcane pressmud used as substrate through solid state fermentation

Efforts were made to utilize the waste/by-product of two agro-process industries namely pressmud from sugar processing industries and spent yeast from distilleries manufacturing ethanol from cane molasses, for the production of microbial invertase. Our experimentation indicated that these two sources could be ideally utilized for the production of invertase through solid substrate fermentation (SSF). SSF with spent yeast had given highest specific activity of 430 U/mg in 72 h of fermentation. Inoculum percentage of yeast cells on pressmud was optimized as 50% (w/w) with a combination inoculum of spent yeast and fresh cultured yeast at a ratio of 7:3. Crude enzyme was characterized for optimum pH and temperature and maximum activity was recorded at pH 5.0 and at a temperature of 40°C. Impacts of metal ions and detergents on invertase action were studied in which Mn²⁺, Fe³⁺, Al³⁺ and detergents had enhanced the activity of the enzyme whereas Cu²⁺ and Zn²⁺ inhibited the enzyme activity. Purification of 9.8 folds was obtained by using three phase partition method.

Growth-dependent secretome of Candida utilis

Recently, the food yeast Candida utilis has emerged as an excellent host for production of heterologous proteins. Since secretion of the recombinant product is advantageous for its purification, we characterized the secreted proteome of C. utilis. Cells were cultivated to the exponential or stationary growth phase, and the proteins in the medium were identified by MS. In parallel, a draft genome sequence of C. utilis strain DSM 2361 was determined by massively parallel sequencing. Comparisons of protein and coding sequences established that C. utilis is not a member of the CUG clade of Candida species. In total, we identified 37 proteins in the culture solution, 17 of which were exclusively present in the stationary phase, whereas three proteins were specific to the exponential growth phase. Identified proteins represented mostly carbohydrate-active enzymes associated with cell wall organization, while no proteolytic enzymes and only a few cytoplasmic proteins were detected. Remarkably, cultivation in xylose-based medium generated a protein pattern that diverged significantly from glucose-grown cells, containing the invertase Inv1 as the major extracellular protein, particularly in its highly glycosylated S-form (slow-migrating). Furthermore, cultivation without ammonium sulfate induced the secretion of the asparaginase Asp3. Comparisons of the secretome of C. utilis with those of Kluyveromyces lactis and Pichia pastoris, as well as with those of the human fungal pathogens Candida albicans and Candida glabrata, revealed a conserved set of 10 and six secretory proteins, respectively.

Influence of micronutrients on yeast growth and β-d-fructofuranosidase production

β-d-fructofuranosidase is one of the most important enzymes of the food industry especially due to its application in preparation of soft centered candies, confectioneries and to produce fructose syrups. Although several bacteria and filamentous fungi are reported for its production, yeasts are the most preferred source for this enzyme. In the present study mineral nutrients were screened for their effect on yeast growth and the enzyme production using Plackett-Burman design. Of the 11 nutrients screened, three variables (KH(2)PO(4), FeCl(3) and CoCl(2)) were significantly effecting yeast growth while six variables, i.e. KH(2)PO(4), CaCl(2), MnSO(4), Na(2)MoO(4), ZnSO(4) and CoCl(2) had significant effect on enzyme production.

Production of thermostable invertases by Aspergillus caespitosus under submerged or solid state fermentation using agroindustrial residues as carbon source

The filamentous fungus Aspergillus caespitosus was a good producer of intracellular and extracellular invertases under submerged (SbmF) or solid-state fermentation (SSF), using agroindustrial residues, such as wheat bran, as carbon source. The production of extracellular enzyme under SSF at 30°C, for 72h, was enhanced using SR salt solution (1:1, w/v) to humidify the substrate. The extracellular activity under SSF using wheat bran was around 5.5-fold higher than that obtained in SbmF (Khanna medium) with the same carbon source. However, the production of enzyme with wheat bran plus oat meal was 2.2-fold higher than wheat bran isolated. The enzymatic production was affected by supplementation with nitrogen and phosphate sources. The addition of glucose in SbmF and SSF promoted the decreasing of extracellular activity, but the intracellular form obtained in SbmF was enhanced 3-5-fold. The invertase produced in SSF exhibited optimum temperature at 50°C while the extra- and intracellular enzymes produced in SbmF exhibited maximal activities at 60°C. All enzymatic forms exhibited maximal activities at pH 4.0-6.0 and were stable up to 1 hour at 50°C.

Evaluation of nitrogenous media components by Plackett–Burman statistical design for β-d-fructofuranosidase production by Saccharomyces sp. strain GVT263

β-d-Fructofuranosidase (FFase), an important enzyme of the confectionery and fructose syrup industry, is produced by several microorganisms. However, yeasts are the most used source because of their high sucrose fermentation capacity. In this work, production of FFase was carried out in submerged fermentation using a high enzyme-producing yeast strain. Plackett–Burman statistical experimental design was applied to evaluate the fermentation medium components. The effects of 10 nitrogen sources were studied in a 16-run experimental design. Beef extract, yeast extract, N-Z-amine, tryptone, meat extract, and ammonium acetate were found to have significant effects on enzyme production. Among these, yeast extract, N-Z-amine, and ammonium acetate were the most significant. A maximum FFase activity of 299.4 U/mL was obtained after a 24 h fermentation period.

Molecular and biochemical characterization of a beta-fructofuranosidase from Xanthophyllomyces dendrorhous

An extracellular beta-fructofuranosidase from the yeast Xanthophyllomyces dendrorhous was characterized biochemically, molecularly, and phylogenetically. This enzyme is a glycoprotein with an estimated molecular mass of 160 kDa, of which the N-linked carbohydrate accounts for 60% of the total mass. It displays optimum activity at pH 5.0 to 6.5, and its thermophilicity (with maximum activity at 65 to 70 degrees C) and thermostability (with a T(50) in the range 66 to 71 degrees C) is higher than that exhibited by most yeast invertases. The enzyme was able to hydrolyze fructosyl-beta-(2-->1)-linked carbohydrates such as sucrose, 1-kestose, or nystose, although its catalytic efficiency, defined by the k(cat)/K(m) ratio, indicates that it hydrolyzes sucrose approximately 4.2 times more efficiently than 1-kestose. Unlike other microbial beta-fructofuranosidases, the enzyme from X. dendrorhous produces neokestose as the main transglycosylation product, a potentially novel bifidogenic trisaccharide. Using a 41% (wt/vol) sucrose solution, the maximum fructooligosaccharide concentration reached was 65.9 g liter(-1). In addition, we isolated and sequenced the X. dendrorhous beta-fructofuranosidase gene (Xd-INV), showing that it encodes a putative mature polypeptide of 595 amino acids and that it shares significant identity with other fungal, yeast, and plant beta-fructofuranosidases, all members of family 32 of the glycosyl-hydrolases. We demonstrate that the Xd-INV could functionally complement the suc2 mutation of Saccharomyces cerevisiae and, finally, a structural model of the new enzyme based on the homologous invertase from Arabidopsis thaliana has also been obtained.

Characterization of a β-fructofuranosidase from Schwanniomyces occidentalis with transfructosylating activity yielding the prebiotic 6-kestose

beta-Fructofuranosidases are powerful tools in industrial biotechnology. We have characterized an extracellular beta-fructofuranosidase from the yeast Schwanniomyces occidentalis. The enzyme shows broad substrate specificity, hydrolyzing sucrose, 1-kestose, nystose and raffinose, with different catalytic efficiencies (k(cat)/K(m)). Although the main reaction catalysed by this enzyme is sucrose hydrolysis, it also produces two fructooligosaccharides (FOS) by transfructosylation. A combination of (1)H, (13)C and 2D-NMR techniques shows that the major product is the prebiotic trisaccharide 6-kestose. The 6-kestose yield obtained with this beta-fructofuranosidase is, to our concern, higher than those reported with other 6-kestose-producing enzymes, both at the kinetic maximum (76gl(-1)) and at reaction equilibrium (44gl(-1)). The total FOS production in the kinetic maximum was 101gl(-1), which corresponded to 16.4% (w/w) referred to the total carbohydrates in the reaction mixture.

Effect of osmotic stress on the derepression of invertase synthesis in nonconventional yeasts

AIMS

The aim of this study was to analyse the effect of osmotic stress on the biosynthesis of invertase enzyme in nonconventional yeasts.

METHODS AND RESULTS

Invertase activities of the nonconventional yeast species belonging to Kluyveromyces, Schwanniomyces and Pichia genus were measured either in the presence or in the absence of various amounts of NaCl. The effect of hyperosmotic stress on the glucose consumption of Saccharomyces cerevisiae and Pichia anomala were also compared. Like S. cerevisiae, derepression of invertase synthesis in Kluyveromyces lactis, Schwanniomyces occidentalis and Pichia jadinii is inhibited by hyperosmotic stress. However, derepression of invertase synthesis in P. anomala is not affected by hyperosmotic stress. In addition, low levels of osmotic stress activated invertase synthesis three- to fourfold in P. anomala and K. lactis.

CONCLUSIONS

This study shows that low levels of osmotic stress induces the invertase synthesis at very high levels in P. anomala and K. lactis. Glucose consumption was not influenced at significant levels by the hyperosmotic stress in P. anomala.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study shows the activation of invertase synthesis by low levels of osmotic stress in P. anomala and K. lactis.