A study of the effect of calcium chloride (CaCl2) and pH on the flocculation ability of Saccharomyces cerevisiae (NCYC 1195)

Xylitol biosynthesis enhancement by Candida tropicalis via medium, process parameter optimization, and co-substrate supplementation

The present study examines the impact of nitrogen sources (yeast extract, ammonium sulfate peptone, ammonium nitrate, urea, and sodium nitrate), salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, 0.3 g/L CaCl2), trace elements solution (0.1 g/L CuSO4, 0.1 g/L FeSO4, 0.02 g/L MnCl2, 0.02 g/L ZnSO4), operational parameters (temperature, aeration, agitation, initial pH and xylose concentration) and co- substrate supplementation (glucose, fructose, maltose, sucrose, and glycerol) on xylitol biosynthesis by Candida tropicalis ATCC 13803 using synthetic xylose. The significant medium components were identified using the Plackett Burman design followed by central composite designs to obtain the optimal concentration for the critical medium components in shaker flasks. Subsequently, the effect of operational parameters was examined using the One Factor At a Time method, followed by the impact of five co-substrates on xylitol biosynthesis in a 1 L bioreactor. The optimal media components and process parameters are as follows: peptone: 12.68 g/L, yeast extract: 6.62 g/L, salt solution (0.5 g/L MgSO4, 0.5 g/L KH2PO4, and 0.3 g/L CaCl2): 1.23 X (0.62 g/L, 0.62 g/L, and 0.37 g/L respectively), temperature: 30 °C, pH: 6, agitation: 400 rpm, aeration: 1 vvm, and xylose: 50 g/L. Optimization studies resulted in xylitol yield and productivity of 0.71 ± 0.004 g/g and 1.48 ± 0.018 g/L/h, respectively. Glycerol supplementation (2 g/L) further improved xylitol yield (0.83 ± 0.009 g/g) and productivity (1.87 ± 0.020 g/L/h) by 1.66 and 3.12 folds, respectively, higher than the unoptimized conditions thus exhibiting the potential of C. tropicalis ATCC 13803 being used for commercial xylitol production.

Yeast assisted algal flocculation for enhancing nutraceutical potential of Chlorella pyrenoidosa

The present research describes yeast assisted algal flocculation followed by evaluation of algae-yeast flocs for nutritional profile as potent food product. Co-flocculation of Chlorella pyrenoidosa using Saccharomyces cerevisiae showed 58.33 ± 2.37% flocculation efficiency. Nutrient composition of algae-yeast flocs (CP-Y) depicted higher protein content (35.52%) as compared to algae (23.72%) and yeast biomass (33.89). Amino acid profiles of CP-Y biomass depicted increase in essential amino acid content with higher ratio of essential to non-essential amino acid (0.68) as compared to Y (0.57) and CP (0.57) biomass. Lipid and carbohydrate content of CP-Y flocs was estimated as 26.95 ± 0.57% and 21.12 ± 0.83%, respectively. Fatty Acid Methyl Esters (FAME) analysis showed presence of omega rich polyunsaturated fatty acids (PUFAs) like α-linolenic acid (ω-3), Linoleic acid (ω-6), Palmitoleic acid (ω-7) etc in CP-Y biomass. The study provides novel insights on nutrition enriched biomass obtained after algal-yeast flocculation, which can be a better alternative to existing flocculation methods for food applications.