Microbial Conversion of Cheese Whey to Polyhydroxybutyrate (PHB) via Statistically Optimized Cultures

The intended circular economy for plastics envisages that they will be partially replaced by bio-based polymers in the future. In this work, natural polyester polyhydroxybutyrate (PHB) was produced Azohydromonas lata using cheese whey (CW) as a low-cost substrate. Initially, CW evaluated sole carbon source PHB production; it found to efficient and comparable production with pure sugars, such saccharose or glucose, even when mild (with dilute acid) hydrolysis of performed instead enzymatic hydrolysis. An additional series experiments statistically designed Taguchi method, dual optimization approach applied maximize intracellular biopolymer content (%PHB, selected quantitative key performance indicator, KPI) weight average molecular (Mw, set qualitative KPI). Two different sets conditions values bioprocess parameters were identified: (1) carbon-to-nitrogen ratio (C/N) 10 w/w, carbon-to-phosphorous (C/P) 1.9 dissolved oxygen concentration (DO) 20%, residence time stationary phase (RT) 1 h, resulting maximum %PHB (61.66% w/w), (2) C/N 13.3 C/P 5 DO RT leading Mw (900 kDa). A final sensitivity analysis confirmed most significant parameter %PHB, whereas important Mw.