Residual Brewing Yeast as Substrate for Co-Production of Cell Biomass and Biofilm Using Candida maltosa SM4

Candida maltosa was cultivated in the liquid phase of residual brewing yeast, a major brewery residue, to produce biomass and biofilm. Using response surface methodology, the effect of two variables at two different levels was investigated. The independent variables were agitation speed (at 100 and 200 rpm), and aeration (at 1 and 3 L min−1). Aeration was identified to be important for the production of both biomass and biofilm, while agitation was the only factor significantly affecting biofilm production. The maximal production of biofilm (2.33 g L−1) was achieved for agitation of 200 rpm and aeration of 1 L min−1, while the maximum for biomass (16.97 g L−1) was reached for 100 rpm agitation and 3 L min−1 air flow. A logistic model applied to predict the growth of C. maltosa in the exponential phase and the biofilm production, showed a high degree of agreement between the prediction and the actual biomass measured experimentally. The produced biofilms were further characterized using Fourier-transform infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Thermogravimetric Analysis (TGA). FTIR allowed the identification of methyl, carbonyl ester and sulfate groups, and revealed the presence of uronic acid moieties and glycosidic bonds. Water-retention ability up to relatively high temperatures was revealed by TGA, and that makes the produced biofilm suitable for production of hydrogels. SEM also gave indications on the hydrogel-forming potential of the biofilm.

Detection of ALS3 and EAP1 gene expresssion in Candida albicans and Candida maltosa biofilms by FISH

Biofilm is regarded as universal forms of microorganism life in aquatic and industrial wastewater systems as well as in a large number of environments and medical devices relevant for public health, where the exact mechanisms by which biofilm-associated microorganisms elicit infection diseases are still poorly understood. Candida biofilm formation is regulated by different mechanisms where adhesins play a clue role in the yeast attachment to certain surfaces. These adhesins are encoding by ALS3, HWP1 and EAP1 genes among others and they are also considered as Candida virulence factors. Methodologies use to study biofilm productions are intended to verify the biofilm composition, formation steps, tridimensional structure and might facilitate the monitoring of biofilm regarding, antibiotic resistance, degradations, inhibitors, enhanciement biofilm formation and other features. Here, FISH expression a modified method to detect gene expression in situ was used in order to detect ALS3, HWP1 and EAP1 in C. albicans and C. maltosa biofilms, constituting a useful tool to monitor biofilm formations. In this regard, ALS3 expression was identified in C. albicans and C. maltosa biofilms.

Candida baotianmanensis sp. nov. and Candida pseudoviswanathii sp. nov., two ascosporic yeast species isolated from the gut of beetles

Four yeast strains were isolated from the gut of beetles collected on Baotianman Mountain and People's Park of Nanyang in Henan Province, China. These strains produced unconjugated asci with one or two ellipsoidal to elongate ascospores in a persistent ascus. Phylogenetic analysis of the D1/D2 domains of the LSU rRNA gene sequences indicated that the isolates represent two novel sexual species in the Candida/Lodderomyces clade. Candida baotianmanensis sp. nov. was located in a statistically well-supported branch together with Candida maltosa. Candida pseudoviswanathii sp. nov. formed a subclade with its closest relative Candida viswanathii supported by a strong bootstrap value. The two novel species were distinguished from their most closely related described species, Candida maltosa and Candida viswanathii, in the D1/D2 LSU rRNA gene and internal transcribed spacer (ITS) sequences and in phenotypic traits. The type strain of Candida baotianmanensis sp. nov. is NYNU 14719T ( = CBS 13915T = CICC 33052T), and the type strain of Candida pseudoviswanathii sp. nov. is NYNU 14772T ( = CBS 13916T = CICC 33053T). The MycoBank numbers for Candida baotianmanensis sp. nov. and Candida pseudoviswanathii sp. nov. are MB 812621 and MB 812622.

Effect of lactic acid on the growth dynamics of Candida maltosa YP1

The growth dynamics of the oxidative imperfect yeast strain Candida maltosa YP1 isolated from the surface of fruit yoghurt was studied in relation to the lactic acid concentration ranging from 0 to 1.6% (w/v). The maximal specific growth rate of 0.36 h^–1 and minimal lag-phase duration of 2.9 h were found in the glucose solution without lactic acid at 25°C. The decrease of the natural logarithm of both the specific growth rate (ln µ) and the lag-phase prolongation (ln ) in the dependence on the increase of lactic acid concentration (0–1.59%) was significantly linear (ln µ = –1.1458 – 0.6056 c; R²_(µ)= 0.9526; ln l = 1.0141 + 1.9766 c; R²₍₎= 0.9577). Based on these equations, the prediction of the time necessary for C. maltosa YP1 to reach 1 × 10⁶ CFU/ml in the dependance on lactic acid concentration and, the initial density of the yeast culture was calculated. For example, C. maltosa YP1 was able to reach the level of 1 × 10⁶ CFU/ml in a model glucose solution at the initial concentration N₀ = 1 CFU/ml, 0.9% lactic acid and 25°C within 2 d. The growth predictions presented indicate a considerable resistance of C. maltosa YP1 to lactic acid in the concentration of up to 1.3% (w/v).