Valorization of the powdered bread waste hydrolysate as growth medium for baker yeast

• Published in: Food and bioproducts processing 2018-05, Vol.109, p.1-8
• Main Authors: Benabda, Olfa, Kasmi, Mariam, Kachouri, Faten, Hamdi, Moktar
• Format: Article
• Language: English
• Subjects: Amylases; Biomass; Biomass production; Bread; Bread waste; Enzymes; Feasibility studies; Fermentation; Flasks; Fungi; Glucoamylase; Growth; Hydrolysate; Inoculation; Kinetics; Microorganisms; Potassium phosphate; Potassium phosphates; Reaction kinetics; Recycling; Saccharomyces cerevisiae; Sugar; Valorization; Waste materials; Yeast; Yeasts; α-Amylase
• ISSN: 0960-3085; 1744-3571
• DOI: 10.1016/j.fbp.2018.02.007

•Large amount of waste bread residues of bakeries can be used to generate microbial biomass without costly pre-treatment.•Bread waste hydrolysates contain valuable components for microbial growth.•At the end of fermentation, the microbial growth reached 2.4×108CFU/ml and sugar and protein depletion exceeded 80%. In this work, the feasibility of baker yeast production using white bread waste is investigated. Grinded and sieved white baguette waste was hydrated and hydrolyzed differently using enzymes preparations to obtain two growth mediums. Medium (I) contained a mixture of alpha amylase and amyloglucosidase; and Medium (II) contained a mixture of alpha amylase, amyloglucosidase and protease enzymes. The clarified media were diluted and supplemented with NH4SO4 (3.5g/l), and KH2PO4 (2g/l). A commercial baker yeast strain was reactivated and a preculture was prepared for the mediums inoculation. Fermentation was carried out in Erlenmeyer flasks and incubated in the thermo-shaker (30°C, 150rpm). After 48h of fermentation, important biomass production was recorded in Mediums (I) and (II) (1.04×108CFU/ml and 2.74×108CFU/ml) compared to the control medium (1.63×108CFU/ml). Hence, the productivity ratio of Medium I and Medium II was estimated to be 0.63 and 1.68. Microbial growth, sugars and proteins consumption kinetics were studied. The obtained results indicated that the production of yeast biomass could be an attractive alternative for bread waste valorization ensuring a global biomass yield of 0.77g/g.