Marine Protists and Rhodotorula Yeast as Bio-Convertors of Marine Waste into Nutrient-Rich Deposits for Mangrove Ecosystems

This paper represents a comprehensive study of two new thraustochytrids and a marine Rhodotorula red yeast isolated from Australian coastal waters for their abilities to be a potential renewable feedstock for the nutraceutical, food, fishery and bioenergy industries. Mixotrophic growth of these species was assessed in the presence of different carbon sources: glycerol, glucose, fructose, galactose, xylose, and sucrose, starch, cellulose, malt extract, and potato peels. Up to 14g DW/L (4.6gDW/L-day and 2.8gDW/L-day) of biomass were produced by Aurantiochytrium and Thraustochytrium species, respectively. Thraustochytrids biomass contained up to 33% DW of lipids, rich in omega-3 polyunsaturated docosahexaenoic acid (C22:6, 124mg/g DW); up to 10.2mg/gDW of squalene and up to 61μg/gDW of total carotenoids, composed of astaxanthin, canthaxanthin, echinenone, and β-carotene. Along with the accumulation of these added-value chemicals in biomass, thraustochytrid representatives showed the ability to secrete extracellular polysaccharide matrixes containing lipids and proteins. Rhodotorula sp lipids (26% DW) were enriched in palmitic acid (C16:0, 18mg/gDW) and oleic acid (C18:1, 41mg/gDW). Carotenoids (87μg/gDW) were mainly represented by β-carotene (up to 54μg/gDW). Efficient growth on organic and inorganic sources of carbon and nitrogen from natural and anthropogenic wastewater pollutants along with intracellular and extracellular production of valuable nutrients makes the production of valuable chemicals from isolated species economical and sustainable.

Triauxic growth of an oleaginous red yeast Rhodosporidium toruloides on waste 'extract' for enhanced and concomitant lipid and β-carotene production

BACKGROUND

Vegetable 'mandi' (road-side vegetable market) waste was converted to a suitable fermentation medium for cultivation of oleaginous yeast Rhodosporidium toruloides by steaming under pressure. This cultivation medium derived from waste was found to be a comparatively better source of nutrients than standard culture media because it provided more than one type of usable carbon source(s) to yeast.

RESULTS

HPLC results showed that the extract contained glucose, xylose and glycerol along with other carbon sources, allowing triauxic growth pattern with preferably usage of glucose, xylose and glycerol resulting in enhanced growth, lipid and carotenoid production. Presence of saturated and unsaturated fatty acid methyl esters (FAMEs) (C_14-20) in the lipid profile showed that the lipid may be transesterified for biodiesel production.

CONCLUSION

Upscaling these experiments to fermenter scale for the production of lipids and biodiesel and other industrially useful products would lead to waste management along with the production of value added commodities. The technique is thus environment friendly and gives good return upon investment.

Microbial lipid production by Cryptococcus curvatus from vegetable waste hydrolysate

This study primarily evaluated the effect of pre-treatment on release of reducing sugars (RS) from vegetable waste (VW). Different acids and alkalis viz., H₂SO₄, HCl, HNO₃, H₃PO₄, NaOH and KOH were evaluated at varied concentration (0.5, 1.0, 1.5 and 2.0%) for pretreatment. The highest RS yield of 472.36 ± 1.89 g/l and 439.13 ± 1.04 g/l was obtained with 1.5% H₂SO₄ and 2% HCl respectively. Secondly, pre-treated vegetable waste hydrolysates (PT-VWH) were evaluated for yeast fermentation using Cryptococcus curvatus MTCC 2698 for lipid production. Maximum biomass (9.46 ± 0.1 g/l and 8.12 ± 0.1 g/l) and lipid (28.3 ± 0.5% and 26 ± 0.5%) was obtained with 1.5% H₂SO₄ PT-VWH and 2% HCl PT-VWH respectively. The FAME profiling revealed the predominance of palmitic, stearic, oleic and linoleic acid. The presence of these fatty acids in majority has beneficial effect on the biodiesel quality.