title: Improvement of lactic acid production in Saccharomyces cerevisiae by a deletion of ssb1.
abstract: Polylactic acid (PLA) is an important renewable polymer, but current processes for producing its precursor, lactic acid, suffer from process inefficiencies related to the use of bacterial hosts. Therefore, improving the capacity of Saccharomyces cerevisiae to produce lactic acid is a promising approach to improve industrial production of lactic acid. As one such improvement required, the lactic acid tolerance of yeast must be significantly increased. To enable improved tolerance, we employed an RNAi-mediated genome-wide expression knockdown approach as a means to rapidly identify potential genetic targets. In this approach, several gene knockdown targets were identified which confer increased acid tolerance to S. cerevisiae BY4741, of which knockdown of the ribosome-associated chaperone SSB1 conferred the highest increase (52%). This target was then transferred into a lactic acid-overproducing strain of S. cerevisiae CEN.PK in the form of a knockout and the resulting strain demonstrated up to 33% increased cell growth, 58% increased glucose consumption, and 60% increased L-lactic acid production. As SSB1 contains a close functional homolog SSB2 in yeast, this result was counterintuitive and may point to as-yet-undefined functional differences between SSB1 and SSB2 related to lactic acid production. The final strain produced over 50 g/L of lactic acid in under 60 h of fermentation.
authors.affiliation: Biomaterials Lab, Samsung Advanced Institute of Technology, 130 Samsung-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do, South Korea.
authors.forename: Jinsuk J
authors.initials: JJ
authors.lastname: Lee
authors.affiliation: McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street Stop C0400, Austin, TX, 78712, USA.
authors.forename: Nathan
authors.initials: N
authors.lastname: Crook
authors.affiliation: McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street Stop C0400, Austin, TX, 78712, USA.
authors.forename: Jie
authors.initials: J
authors.lastname: Sun
authors.affiliation: McKetta Department of Chemical Engineering, The University of Texas at Austin, 200 East Dean Keeton Street Stop C0400, Austin, TX, 78712, USA. halper@che.utexas.edu.
authors.forename: Hal S
authors.initials: HS
authors.lastname: Alper
mesh_terms: D005285:Fermentation; D055785:Gene Knockdown Techniques; D018840:HSP70 Heat-Shock Proteins / Q000172:deficiency* / Q000235:genetics*; D019344:Lactic Acid / Q000096:biosynthesis* / Q000737:chemistry; D060847:Metabolic Engineering; D011091:Polyesters; D011108:Polymers / Q000737:chemistry; D034622:RNA Interference; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics*
chemical_list: D018840:HSP70 Heat-Shock Proteins; D011091:Polyesters; D011108:Polymers; C095192:SSB1 protein, S cerevisiae; D029701:Saccharomyces cerevisiae Proteins; D019344:Lactic Acid; C033616:poly(lactide)
keywords: Acid tolerance; Genome-wide knockdown library; Lactic acid; RNA interference; SSB1; Yeast