Yeast strains from coconut toddy in Sri Lanka show high tolerance to inhibitors derived from the hydrolysis of lignocellulosic materials

Abstract

We previously isolated 18 Saccharomyces cerevisiae strains from coconut toddy in Sri Lanka. All the 18 strains (SLY-1 to SLY-18) could grow aerobically up to 18 mmol L À1 vanillin in yeast extract-peptone-dextrose (YPD) medium, and the SLY-10 strain showed the highest vanillin tolerance (up to 21 mmol L À1 ). Among these 18 strains, even in the presence of 24 mmol L À1 vanillin, five strains (SLY-3, SLY-4, SLY-8, SLY-9 and SLY-10) produced alcohol at 72 h in the range of 11.4-33.1 g L À1 and the SLY-10 strain showed highest alcohol production. The five strains showed the conversion of vanillin to vanillyl alcohol. They also tolerated other strong inhibitors: 4-hydroxybenzoic acid (24 mmol L À1 ), furfural (30 mmol L À1 ), 5-hydroxymethyl-2-furaldehyde (5-HMF, 36 mmol L À1 ) and acetic acid (75 mmol L À1 ). All these five strains showed no growth and no alcohol production when cultured in the medium with inhibitor mixture of 2.7 mmol L À1 vanillin, 30 mmol L À1 furfural, 30 mmol L À1 5-HMF, 75 mmol L À1 acetic acid and 75 mmol L À1 formic acid but showed significant growth and alcohol production of 16.2-32.7 g L À1 with inhibitor mixture of 30% concentration (0.81 mmol L À1 vanillin, 9 mmol L À1 furfural, 9 mmol L À1 5-HMF, 22.5 mmol L À1 acetic acid and 22.5 mmol L À1 formic acid). The four strains (SLY-3, SLY-4, SLY-8 and SLY-9) were shown to tolerate the inhibitor mixture to a similar extent and better than SLY-10, while SLY-10 was the best to vanillin alone. ARTICLE HISTORY

Promising Renewable Raw for Ethanol Biosynthesis

“…To transform this rigid crystalline structure from microfibrils in the cell wall into an amorphous structure in water, high temperature and pressure conditions are required at 320 °C and 25 MPa, respectively. These requirements are obviously higher than for starchy raw materials (Subodinee et al, 2019).…”

“…Many studies have looked for S. cerevisiae strains with higher resistance to salt and temperature (Tekarslan-Sahin et al, 2018;Subodinee et al, 2019;Lip et al, 2020). Schizosaccharomyces pombe yeast is also used for bioethanol production as it withstands high salt concentrations and high solids content.…”

“…Schizosaccharomyces pombe yeast is also used for bioethanol production as it withstands high salt concentrations and high solids content. In the production of bioethanol, the possibility of using other microorganisms, such as Zymomonas mobilis, Klebsiella oxytoca, E. coli, Thermoanaerobacter ethanolicus, Pichia stipitis, Candida shehatae, Mucor indicus, was investigated (Subodinee et al, 2019). However, no adequate alternative to S. cerevisiae has yet been found.…”

Single Cell Protein Production Using Different Fruit Waste: A Review

“…Lignocellulosic materials contain 70% carbohydrates, mainly cellulose and hemicellulose, which require pre-treatment in order to convert carbohydrates to fermentable sugars. These pre-treatments generate numerous by-products that are toxic to yeast cells, such as phenolic compounds including vanillin and 4-hydroxybenzoic acid (PHBA), furan derivatives, like 5-hydroxymethyl-2-furaldehyde (5-HMF) and furfural and weak acids (acetic acid and formic acid) [51].…”