Honey's Yeast-New Source of Valuable Species for Industrial Applications.

Honey is a rich source of compounds with biological activity; moreover, it is a valuable source of various microorganisms. The aim of this study was to isolate and identify yeast from a sample of lime honey from Poland as well as to assess its ability to biosynthesize value-added chemicals such as kynurenic acid, erythritol, mannitol, and citric acid on common carbon sources. Fifteen yeast strains belonging to the species Yarrowia lipolytica, Candida magnolia, and Starmerella magnoliae were isolated. In shake-flask screening, the best value-added compound producers were chosen. In the last step, scaling up of the culture in the bioreactor was performed. A newly isolated strain of Y. lipolytica No. 12 produced 3.9 mg/L of kynurenic acid growing on fructose. Strain Y. lipolytica No. 9 synthesized 32.6 g/L of erythritol on technical glycerol with a low concentration of byproducts. Strain Y. lipolytica No. 5 produced 15.1 g/L of mannitol on technical glycerol, and strain No. 3 produced a very high amount of citric acid (76.6 g/L) on technical glycerol. In conclusion, to the best of our knowledge this is the first study to report the use of yeast isolates from honey to produce valuable chemicals. This study proves that natural products such as lime honey can be an excellent source of wild-type yeasts with valuable production properties.

The microbial production of kynurenic acid using Yarrowia lipolytica yeast growing on crude glycerol and soybean molasses.

Yarrowia lipolytica yeast are able to produce kynurenic acid-a very valuable compound acting as a neuroprotective and antioxidant agent in humans. The recent data proved the existence of the kynurenine biosynthesis pathway in this yeast cells. Due to this fact, the aim of this work was to enhance kynurenic acid production using crude glycerol and soybean molasses as cheap and renewable carbon and nitrogen sources. The obtained results showed that Y. lipolytica GUT1 mutants are able to produce kynurenic acid in higher concentrations (from 4.5 mg dm-3 to 14.1 mg dm-3) than the parental strain (3.6 mg dm-3) in the supernatant in a medium with crude glycerol. Moreover, the addition of soybean molasses increased kynurenic acid production by using wild type and transformant strains. The A-101.1.31 GUT1/1 mutant strain produced 17.7 mg dm-3 of kynurenic acid in the supernatant during 150 h of the process and 576.7 mg kg-1 of kynurenic acid in dry yeast biomass. The presented work proves the great potential of microbial kynurenic acid production using waste feedstock. Yeast biomass obtained in this work is rich in protein, with a low content of lipid, and can be a healthy ingredient of animal and human diet.