Yeast Candida Utilis Research Articles

How do the carbon and nitrogen sources affect the synthesis of β-(1,3/1,6)-glucan, its structure and the susceptibility of Candida utilis yeast cells to immunolabelling with β-(1,3)-glucan monoclonal antibodies?

BackgroundThe need to limit antibiotic therapy due to the spreading resistance of pathogenic microorganisms to these medicinal substances stimulates research on new therapeutic agents, including the treatment and prevention of animal diseases. This is one of the goals of the European Green Deal and the Farm-To-Fork strategy. Yeast biomass with an appropriate composition and exposure of cell wall polysaccharides could constitute a functional feed additive in precision animal nutrition, naturally stimulating the immune system to fight infections.ResultsThe results of the research carried out in this study showed that the composition of Candida utilis ATCC 9950 yeast biomass differed depending on growth medium, considering especially the content of β-(1,3/1,6)-glucan, α-glucan, and trehalose. The highest β-(1,3/1,6)-glucan content was observed after cultivation in deproteinated potato juice water (DPJW) as a nitrogen source and glycerol as a carbon source. Isolation of the polysaccharide from yeast biomass confirmed the highest yield of β-(1,3/1,6)-glucan after cultivation in indicated medium. The differences in the susceptibility of β-(1,3)-glucan localized in cells to interaction with specific β-(1,3)-glucan antibody was noted depending on the culture conditions. The polymer in cells from the DPJW supplemented with glycerol and galactose were labelled with monoclonal antibodies with highest intensity, interestingly being less susceptible to such an interaction after cell multiplication in medium with glycerol as carbon source and yeast extract plus peptone as a nitrogen source.ConclusionsObtained results confirmed differences in the structure of the β-(1,3/1,6)-glucan polymers considering side-chain length and branching frequency, as well as in quantity of β-(1,3)- and β-(1,6)-chains, however, no visible relationship was observed between the structural characteristics of the isolated polymers and its susceptibility to immunolabeling in whole cells. Presumably, other outer surface components and molecules can mask, shield, protect, or hide epitopes from antibodies. β-(1,3)-Glucan was more intensely recognized by monoclonal antibody in cells with lower trehalose and glycogen content. This suggests the need to cultivate yeast biomass under appropriate conditions to fulfil possible therapeutic functions. However, our in vitro findings should be confirmed in further studies using tissue or animal models.

A Bioethanol Waste Challenge being a Source of High-Quality ProteinRich Feedstock: A New Technology

Microbial biomass protein from Candida utilis yeast was produced using distillery vinasse as the sole source of carbon and energy. The process was carried out from lab scale to 200 m3 fermentors. Propagation media have to be supplemented with nutrients since vinasse cannot provide all compounds needed for a stable operation. Different mixtures of molassesenriched vinasse were tested and finally, a Microbial Growth Enhancer (MGE) was incorporated into the media to ensure its optimization. MGE-supplemented vinasse at 0.03 kgm3 was found optimum for yeast propagation. At an industrial scale, µmax ≥ 0.33 h-1 was obtained which allowed a stable behavior of the culture at this scale and significant industrial productivity. Yeast biomass from vinasse showed a composition and amino acid profile very similar to those previously obtained from molasses medium. Nutritional tetestsemonstrated that vinasse´s yeast is an excellent source of proteins for animal feeding and an efficient pollution reducer.

Ammonia nitrogen recovery from biogas slurry by SCP production using Candida utilis

The safe and robust yeast Candida utilis was employed for nitrogen recovery as single cell protein from biogas slurry. The maximum biomass of 6.2 g/L with protein content of 53.5% was produced in batch cultivation with glucose as the carbon source, C/N ratio of 3:1, NH4+-N concentration of 3000 mg/L, initial pH of 8.0, and the addition of 0.35% (w/v) Na2HPO4. It was speculated that C. utilis can grow well with free ammonia below 197 mg/L. In fed-batch fermentation, a biomass of 14.8 g/L was obtained, and the maintenance of aerobic conditions was critical to improving the production of single cell protein. The sterilized and non-sterilized biogas slurry can be used as an effective pH regulator. The obtained single cell protein was a nutritious, safe, and reliable protein source. This study provides novel insights into nitrogen recovery via C. utilis as a single cell protein from biogas slurry.

Rice husk integrated biochemical refinery for the production of nano- and bioproducts

Rice husk contains high contents of cellulose, lignin, and inorganic compounds, which can be recovered and utilized in a variety of useful applications. In this study, rice husk was refined using a multistage process for producing nano- and bioproducts. To begin, the material was treated with dilute sulfuric acid for obtaining a pentose solution, which was then used for Candida utilis yeast fermentation. In the next stage, the pre-hydrolyzed rice husk was treated with an alkaline solution under regular pulping conditions to break down all chemical bonds between the substances in the material. Subsequently, cellulose was extracted for nanocellulose production, while lignin and silica were isolated via acid precipitation. Proper conditions for these processes were established. Under suitable conditions, about 55.0% of the rice husk was effectively utilized. Over 75.0% of the rice husk pentosan was converted into xylose and arabinose for single-cell protein fermentation. Lignin was mostly transformed into lower molecular weight compounds or single substances, resulting in a recovery rate of about 17.0%. The precipitation’s pH for silica and lignin recovery was 8.5 and 3.0, respectively. The findings of this work provide an effective solution for the utilization of agricultural residue and contribute significantly to the sustainable development.

Fungaemia due to rare yeasts in paediatric intensive care units: A prospective study.

Considering the emergence of fungaemia due to rare yeasts at our centre, we performed a systematic epidemiologic study on fungaemia due to rare yeast. We undertook the present prospective observational study to explore the epidemiological features and clinical characteristics of fungaemia due to rare yeasts in paediatric ICUs at our centre. The successive yeasts isolated from blood at our PICUs during December 2017 through March 2019 were identified by molecular methods. Fungaemia due to yeasts other than C.albicans, C.tropicalis, C.glabrata, C.krusei and C.parapsilosis was categorised as rare yeasts. Antifungal susceptibility testing of the yeast isolates was performed as per clinical and laboratory standards institute (CLSI) guidelines. We also compared different clinical parameters of fungaemia due to common versus rare yeasts, and rare yeasts in neonates versus non-neonates. During the study period, 212 yeast isolates were obtained from 159 patients at PICUs of our hospital, and 127 isolates from 98 patients (61.6%) were categorised as rare yeasts. Neonates acquired fungaemia significantly earlier after ICU admission than non-neonates (median:4 vs 6days; p=.005). Regarding epidemiology study of rare yeast fungaemia, Wickerhamomyces anomalus (43.8%) and Candida utilis (40.8%) were common isolates; surgical intervention and gastrointestinal disease were significantly associated; overall, azole, echinocandin and amphotericin B resistance was at 9.1%, 1.02% and 1.02%, respectively; overall mortality was 65.3%. The emergence of rare yeasts especially W.anomalus and C.utilis causing fungaemia in our children demands urgent attention to control the spread.

Evaluation of different food attractants for capture of Lonchaeidae (Diptera: Tephritoidea) in passion fruit orchard in southern Santa Catarina state, Brazil

Brazil is the world’s largest producer and consumer of yellow passion fruit, Passiflora edulis Sims (Passifloraceae). Among the insects identified as pests associated with passion fruit, Lonchaeidae flies are of great economic importance because they damage floral buds, thereby affecting fruit development and causing production losses. However, there is no recommended monitoring system that uses traps and attractants. Thus, this study, conducted in a commercial crop, aimed to evaluate the efficiency of different food attractants in McPhail traps in the capture of Lonchaeidae to promote integrated management programs for these flies. The results showed that the attractants torula yeast (Candida utilis) and hydrolyzed protein of animal origin (Cera Trap®) were the most efficient in the capture of Lonchaeidae flies. From an economic point of view, the use of torula yeast would be recommended since this product is cheaper to purchase. This is the first study to determine the efficiency of Cera Trap® in the capture of lonchaeids in passion fruit orchards.

Metabolic Response of the Yeast Candida utilis During Enrichment in Selenium.

Selenium (Se) was found to inhibit the growth of the yeast Candida utilis ATCC 9950. Cells cultured in 30 mg selenite/L supplemented medium could bind 1368 µg Se/g of dry weight in their structures. Increased accumulation of trehalose and glycogen was observed, which indicated cell response to stress conditions. The activity of antioxidative enzymes (glutathione peroxidase, glutathione reductase, thioredoxin reductase, and glutathione S-transferase) was significantly higher than that of the control without Se addition. Most Se was bound to water-insoluble protein fraction; in addition, the yeast produced 20–30 nm Se nanoparticles (SeNPs). Part of Se was metabolized to selenomethionine (10%) and selenocysteine (20%). The HPLC-ESI-Orbitrap MS analysis showed the presence of five Se compounds combined with glutathione in the yeast. The obtained results form the basis for further research on the mechanisms of Se metabolism in yeast cells.

Cu-Al mixed oxide-catalysed multi-component synthesis of gluco- and allofuranose-linked 1,2,3-triazole derivatives.

A series of carbohydrate-linked 1,2,3-triazole derivatives were synthesized in good yields from glucofuranose and allofuranose diacetonides using as key step a three-component 1,3-dipolar azide–alkyne cycloaddition catalysed by a Cu–Al mixed oxide. In this multi-component reaction, Cu–Al mixed oxide/sodium ascorbate system serves as a highly reactive, recyclable and efficient heterogeneous catalyst for the regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles. The reported protocol has significant advantages over classical CuI/N,N-diisopropylethylamine (DIPEA) or CuSO4/sodium ascorbate conditions in terms of efficiency and reduced synthetic complexity. In addition, the selective deprotection of synthesized di-O-isopropylidene derivatives was also carried out leading to the corresponding mono-O-isopropylidene products in moderate yields. Some of the synthesized triazole glycoconjugates were tested for their in vitro antimicrobial activity using the disc diffusion method against Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), as well as fungus (Aspergillus niger) and yeast (Candida utilis). The results revealed that these compounds exhibit moderate to good antimicrobial activity mainly against Gram-negative bacteria.

The ploidy determination of the biotechnologically important yeast Candida utilis.

Yeast Candida utilis is considered to be a potentially advantageous expression system for production of recombinant proteins utilizable for industrial and pharmaceutical purposes. As the scientific literature is not consistent in the ploidy of this yeast, in this work, we focused on resolving the problem via several methods such as the copy number determination of maltase gene by multiplex PCR, measuring α-glucosidase activity, the characterization of maltase gene copy number in deletion mutants using qPCR and flow cytometry. In context with the published data and results obtained in this study about the copy number of the maltase gene on C. utilis genome, we attempted to hypothesise and made conclusion about the ploidy of C. utilis. The results of this work, besides the biotechnological aspect, contribute to the elementary knowledge of C. utilis. The exact information about the ploidy or more specifically about the copy number of appropriate gene is essential for expression cassette dosage determination integrated into the chromosome of the host. In this study, we come to the conclusion that the maltase gene is present in C. utilis genome in four alleles, and in combination with flow cytometry, published information and the published genome sequences, the observations support the theory about tetraploidy of C. utilis.

Candida utilis yeast as a functional protein source for Atlantic salmon (Salmo salar L.): Local intestinal tissue and plasma proteome responses.

Microbial ingredients such as Candida utilis yeast are known to be functional protein sources with immunomodulating effects whereas soybean meal causes soybean meal-induced enteritis in the distal intestine of Atlantic salmon (Salmo salar L.). Inflammatory or immunomodulatory stimuli at the local level in the intestine may alter the plasma proteome profile of Atlantic salmon. These deviations can be helpful indicators for fish health and, therefore potential tools in the diagnosis of fish diseases. The present work aimed to identify local intestinal tissue responses and changes in plasma protein profiles of Atlantic salmon fed inactive dry Candida utilis yeast biomass, soybean meal, or combination of soybean meal based diet with various inclusion levels of Candida utilis. A fishmeal based diet was used as control diet. Inclusion of Candida utilis yeast to a fishmeal based diet did not alter the morphology, immune cell population or gene expression of the distal intestine. Lower levels of Candida utilis combined with soybean meal modulated immune cell populations in the distal intestine and reduced the severity of soybean meal-induced enteritis, while higher inclusion levels of Candida utilis were less effective. Changes in the plasma proteomic profile revealed differences between the diets but did not indicate any specific proteins that could be a marker for health or disease. The results suggest that Candida utilis does not alter intestinal morphology or induce major changes in plasma proteome, and thus could be a high-quality alternative protein source with potential functional properties in diets for Atlantic salmon.

Yeast as a protein source during smoltification of Atlantic salmon (Salmo salar L.), enhances performance and modulates health

Yeast produced from lignocellulosic biomass has the potential to serve as a high-quality protein source with health benefits, especially during critical stages of the Atlantic salmon life cycle, such as during seawater transfer (SWT). In this study, we evaluated the effect of adding 25% Candida utilis yeast to salmon feed on growth performance and overall health by using morphometry, immunohistochemistry, cytokine enzyme-linked immunosorbent assays (ELISA) and gene expression analysis during and after SWT. There were four dietary treatments: 1) control diet in freshwater (FW) and seawater (SW) (Control); 2) control diet in FW and a yeast-based diet in SW (Control/Yeast); 3) yeast-based diet in FW and SW (Yeast); 4) yeast-based diet in FW and a control diet in SW (Yeast/Control). Our results showed that fish fed the yeast diet throughout the FW and SW period achieved higher feed intake and higher growth rate than fish fed the control diet. Morphometric and immunochemical analyses of the distal intestine (DI) revealed decreased length and number of CD3 labeled cells in the simple folds of fish fed control diet, while no changes were observed in fish fed the yeast diet. Furthermore, yeast significantly decreased the secretion of IFNγ, TNFα, IL-1β, IL-8, and modulated the gene expression of aquaporin 8 (aqp8ab), superoxide dismutase (sod1) and major histocompatibility complex 1 (mhc1) in DI, suggesting reduced inflammatory processes in yeast fed fish. These findings indicate that Candida utilis yeast is a promising alternative protein source with functional properties in diets for smolting Atlantic salmon before and after SWT.

Phosphorus-rich microorganism-enabled synthesis of cobalt phosphide/carbon composite for bisphenol A degradation through activation of peroxymonosulfate

Phosphorus (P) recovery is of significant importance due to its limited reserves and non-regenerative nature. In this study, we attempted to recover and utilize P from microorganism to obtain metal phosphide/carbon composites. By P-rich cultivation of a model yeast (Candida utilis), a total 4.3 wt% P could be accumulated in microorganism. A hydrothermal treatment coupled with pyrolysis approach enabled the formation of cobalt phosphide/carbon (Co2P/C) composites using P-rich microorganism and Co2+ as precursors. Thermogravimetric-mass spectrometry (TG-MS) analysis confirmed the generation of reducing gases (CO, CH4, PH3, etc.) in pyrolysis process, which played important roles for the conversion of phosphate (in microorganism) to phosphide (in Co2P). When adopted as catalyst for peroxymonosulfate (PMS) activation, the developed Co2P/C composite performed well for bisphenol A (BPA) degradation with a 97.8% removal efficiency in 30 min. The recyclability of Co2P/C was also evident by five successive recycle runs. Moreover, intermediates in BPA degradation process were identified by gas chromatography-mass spectrometry (GC–MS) and liquid chromatography-mass spectrometry (LC-MS), which allowed us to propose a BPA degradation pathway. The following preliminary ecotoxicity test using Tetraselmis subcordiformis as ecological indicator confirmed that BPA degradation solution was much less toxic than the original solution. The strategy proposed in this study, which is the utilization of integrated elements (P, C, etc.) in microorganism to develop efficient catalyst, may provide a new solution for the recovery and value-added conversion of biomass/biowaste.

Candida utilis yeast as a protein source for weaned piglets: Effects on growth performance and digestive function

Yeast such as inactivated Candida utilis produced from lignocellulosic biomass from underutilized wood co-products as a second-generation sugar source is a potentially sustainable protein feed ingredient in diets for piglets. This study aimed to evaluate the effects of C. utilis added to diets for weaned piglets on growth performance and digestive function when replacing main protein sources. Forty-eight piglets weaned at 30 days of age, with a mean starting weight of 11.06 ± 0.84 kg were fed one of four dietary treatments for 28 days: a conventional control diet with soybean meal, fishmeal, rapeseed meal, and potato protein or one of three experimental diets containing 10, 20 or 40% crude protein (CP) from yeast (CU10, CU20, and CU40, respectively). Adding yeast to diets did not affect growth performance compared with the control. The diet with 40% CP from C. utilis had higher apparent total tract digestibility (ATTD) of CP compared with the control (P = 0.034) and higher ATTD of ash (P < 0.001) compared with the control. The ATTD of neutral detergent fiber decreased in the CU40 diet compared with the control (P = 0.006). The apparent ileal digestibility (AID) of ash increased (P = 0.001) in the CU40 diet compared with the control, while the AID of CP and amino acids was unaffected. Villi-height increased in jejunum (P = 0.007) and ileum (P = 0.047), and villus-height: crypt-depth ratio increased (P = 0.001) in jejunum of piglets fed the CU40 diet compared with the control. Fecal dry matter increased linearly with increasing levels of C. utilis in the diets at day 7 after weaning (P = 0.001) and was higher for the CU40 group compared with the control group at day 21 after weaning (P = 0.027). Trypsin activity and messenger RNA expression of nine genes encoding for nutrient transporters in the jejunum did not differ among diets. Collectively, the results indicated that C. utilis can replace 40% of CP from the main protein sources traditionally used in diets for weaned piglets while maintaining growth and improving digestive function.

Production and Optimization of the Extraction Conditions of a Biosurfactant of Candida Utilis Ufpeda1009 with Potential of Application in the Food Industry

Biosurfactants are amphipathic molecules with capacity to reduce the surface and interfacial tension of aqueous solutions, arousing great industrial interest due to the diversity of structures and production from renewable sources, allowing the obtention of products with unique characteristics. In the food industry, for example, the use of biosurfactants produced by some yeasts is very promising, since they do not present any risk of toxicity and pathogenicity, and can be applied in emulsification, for improvement of mass texture, as antimicrobial agents and in the replacement of fats. Thus, the aim of this work was to produce a biosurfactant by the yeast Candida utilis UFPEDA1009 with potential application as an emulsifier in foods. The yeast was grown in mineral medium containing 6% canola frying oil and 6% glucose, under 150 rpm agitation for 88 h at 28 °C. After the production process, the surface and interfacial tension, yield and Critical Micelle Concentration (CMC), as well as the particle size distribution of emulsions were determined. The surface and interfacial tensions obtained were, respectively, 35.33 ± 0.19 and 2.53 ± 0.02 mN/m, with biosurfactant yield varying from 13.10 ± 0.04 to 48. 05 ± 0.21 g/L. The biosurfactant CMC was 0.6 g/L. The emulsions showed small particle sizes, with uniform shape and more separated particles, appearing resistance to coalescence. In general, it was observed that the increase in the concentration of the biosurfactant resulted in the decrease of the particle size, that is, the higher the concentration of a given biosurfactant, the greater the stability of the emulsion. The microbial surfactant was incorporated in the mass of a biscuit formulation in substitution of the animal fat, which showed improvements in the texture profile of its mass. Therefore, the biosurfactant produced is promising for application in food formulations as an emulsifier.

Torula yeast (Candida utilis)-derived glucosylceramide contributes to dermal elasticity in vitro.

Glucosylceramide (GlcCer) is derived from several plants, such as rice, maize, and wheat, and has been reported to retain moisture by functioning as a barrier between the epidermis and the environment. However, there is insufficient research on the effect of GlcCer on dermal elasticity and wrinkles. In this study, we investigated the effects of torula yeast extract and torula yeast-derived GlcCer on dermal elasticity. We measured cell proliferation, collagen production, and collagen gel contraction using human dermal fibroblasts. Torula yeast extract and torula yeast-derived GlcCer increased dermal fibroblast proliferation and collagen production. Collagen gel contraction was promoted by torula yeast extract and torula yeast-derived GlcCer. These results indicate that GlcCer may affect dermal elasticity. Torula yeast extract and torula yeast-derived GlcCer may contribute to the maintenance of dermal elasticity. PRACTICAL APPLICATIONS: In this study, we found that torula yeast-derived glucosylceramide (GlcCer) has an additional function of improving dermal elasticity. With improved elasticity, skin becomes more resilient, thus preventing wrinkles. GlcCer has already been used in cosmetic products to retain skin moisture. Therefore, torula yeast-derived GlcCer can be expected to have several cosmetic applications.

Backset valorization in dry-grind ethanol process by co-culture of edible filamentous fungi and fodder yeast

In this study, edible filamentous fungi Aspergillus oryzae and Rhizopus oligosporus were co-cultured with fodder yeast Candida utilis using corn thin stillage to produce feed-grade biomass, amylases, and ethanol with the purpose of backset valorization. The co-culture of A. oryzae with C. utilis inoculated after 24 h of pure fungal growth provided the most promising results, yielding 18.6 g L−1 biomass with 41 and 31% of lipid and protein, respectively, with all of the essential amino acids. The microorganisms consumed nearly 34% of the cultivation medium solids, as well as 33% of glycerol and 12% of lactic acid, which allowed them to produce ca. 4.5 g L−1 ethanol and 1.7 U mL−1 amylase. The liquid fraction of the cultivation medium was used as 200 mL L−1 backset for the production of high-solids corn mash. The final ethanol concentrations reached 78.3, 90.6 and 108.2 g L−1 in the control sample (without backset), unfermented backset addition and fermented backset addition, respectively. This suggests that the yeast-fungi co-culture for backset treatment was effective in improving the core production stage in an ethanol-producing plant.

Speciation Analysis of Selenium in Candida utilis Yeast Cells Using HPLC-ICP-MS and UHPLC-ESI-Orbitrap MS Techniques

Selenium plays a key role in the proper metabolism of living organisms. The search for new selenium compounds opens up new possibilities for understanding selenometabolome in yeast cells. This study was aimed at the identification of compounds containing selenium in the feed yeasts Candida utilis ATCC 9950. Yeast biomass was kept in aqueous solutions enriched with inorganic selenium (20 mg·L−1) for 24 h. Speciation analysis of the element was performed using the HPLC-ICP-MS and UHPLC-ESI-Orbitrap MS techniques. The obtained selenium value in the yeast was 629 μg·g−1, while the selenomethionine value was 31.57 μg·g−1. The UHPLC-ESI-Orbitrap MS analysis conducted allowed for the identification of six selenium compounds: dehydro-selenomethionine-oxide, selenomethionine, selenomethionine-NH3, a Se-S conjugate of selenoglutathione-cysteine, methylthioselenoglutathione, and 2,3-DHP-selenocysteine-cysteine. In order to explain the structure of selenium compounds, the selected ions were subjected to fragmentation. The selenium compounds obtained with a low mass play a significant role in the metabolism of the compound. However, the bioavailability of such components and their properties have not been fully understood. The number of signals indicating the presence of selenium compounds obtained using the UHPLC-ESI-Orbitrap MS method was characterized by higher sensitivity than when using the HPLC-ICP-MS method. The obtained results will expand upon knowledge about the biotransformation of selenium in eukaryotic yeast cells. Future research should focus on understanding the entire selenium metabolism in cells and on the search for new transformation pathways for this element. This opens up new possibilities for obtaining functional food, rich in easily absorbable selenium sources, and constituting an alternative to dietary supplements based on this compound found primarily in inorganic form.

Microbial Protein Produced from Brown Seaweed and Spruce Wood as a Feed Ingredient.

The conversion of nonedible biomass to protein for use in feed is an attractive strategy toward improved sustainability in aquaculture. We have studied the possibility to produce protein-rich yeast Candida utilis on a medium consisting of enzymatically hydrolyzed sulphite-pulped spruce wood, mainly providing glucose, and enzymatically hydrolyzed brown seaweed, supplemented with ammonium sulfate. The results show that this blend constitutes a complete fermentation medium that enables good growth rates and cell yields. Results from a salmon feeding trial showed that the yeast can replace parts of a traditional fishmeal diet without harmful effects, although the apparent protein digestibility coefficient for the yeast was suboptimal. While further optimization of both the fermentation process and downstream processing is needed, the present proof-of-concept study shows a path to the production of microbial protein based on a simple, local and sustainable fermentation medium.

Antimicrobial Efficiency of Metallurgical Slags for Application in Building Materials and Products

The article deals with studying the antimicrobial efficiency of finely ground metallurgical slags, such as granulated blast-furnace slag with specific surface areas of 340 (1Sa) and 520 m2/kg (1Sb), air cooled blast-furnace slag (2S), demetallized steel slag (3S), calcareous ladle slag (4S), and copper slag (5S). The efficiency was tested on microbial representatives, such as: Gram-positive bacteria—Bacillus subtilis, Staphylococcus aureus, Micrococcus luteus; Gram-negative bacteria—Escherichia coli, Pseudomonas aeruginosa, Serratia marcescens; yeasts—Candida utilis, Rhodotorula glutinis; and microscopic filamentous fungi—Aspergillus niger, Penicillium funiculosum, Chaetomium globosum, Alternaria alternata, Trichoderma viride, Cladosporium herbarum. The efficiency was determined by dilution methods in agar growth media so that the resulting concentration of the tested slags was 10, 20, 40, and 60%. The antibacterial efficiency of the slags decreased in the order: S4 &gt; S3 &gt; S2 &gt; S1a = S1b &gt; S5, while their anti-yeast efficiency decreased in the order S4 &gt; S1a = S1b = S3 &gt; S2 &gt; S5. Microscopic filamentous fungi were selectively sensitive to the slags; therefore, there is only an approximate order of efficiency of S4 &gt; S3 = S1a = S1b &gt; S5 &gt; S2. Application of metallurgical slags into building materials and products provide them with increasing resistance against biodeterioration.

Simultaneous saccharification and cultivation of Candida utilis on cassava peel

Candida utilis yeast, a rich source of proteins and vitamin B-complex was cultivated on cassava peel, a food processing waste, which was first liquefied with Termamyl 120 L α-amylase enzyme. The cultivation process was optimized simultaneously with saccharification with Novo AMG 300 L amyloglucosidase using response surface methodology approach. The design involved three duration of enzyme hydrolysis (0, 4.5 and 9 h) prior to inoculation with Candida utilis representing varied degrees of hydrolysis (0, 50 and 100%) and initial pH (4.5, 5.0 and 5.5). Measured responses were change in yeast protein ranging from 1.13 to 1.91 mg/mL, change in cell concentration ranging from 2.30 to 3.90 mg/mL and specific growth rate ranging from 0.21–0.51.100% hydrolysis and initial pH of 5.0 gave the highest changes in yeast protein (1.92 mg/mL) and cell concentration (3.90 mg/mL); 100% hydrolysis and pH 5.5 gave the highest specific growth rate. The optimal solution was obtained at pH of 5.5 and 100% degree of hydrolysis with a degree of desirability of 0.8. The cultivation of Candida utilis yeast on cassava peel is of high significance to food and agro-based industries for the production of value added products, waste disposal and valorisation. Cassava peel is a major waste product from cassava processing industry which is faced with an enormous challenge regarding its disposal. This study revealed that Candida utilis can be cultivated successfully on cassava peel slurry; the cultivation of this yeast on cassava peel is of high significance to food and agro-based industries for the production of value added products waste disposal and valorisation.