Metabolic Responses of Candida viswanathii on Lipase Production: Influence of Carbon Sources and Culture System

Microbial lipases are pivotal biocatalysts in the food, pharmaceutical, and bioenergy industries due to their versatility and stability. Among potential producers, the yeast Candida viswanathii has shown promise, yet the transition from laboratory shake flasks to stirred tank bioreactors often presents challenges due to altered physiological and metabolic responses. Specifically, determining how different carbon sources influence the trade-off between biomass growth and enzyme secretion during this scale-up remains a critical bottleneck. Here we show that while sorbitol acts synergistically with soybean oil to maximize lipase production in shake flasks (13.56 U mL^-1), it triggers a strong inhibitory effect on enzyme expression when scaled up to a stirred tank bioreactor. Contrary to the expectation that optimized flask conditions would translate linearly, the bioreactor environment shifted the yeast's metabolism toward rapid biomass accumulation (30 g L^-1) at the expense of lipolytic activity, with the highest reactor yields achieved only in the absence of sorbitol (13.56 U mL^-1). These findings underscore the necessity of re-evaluating medium composition specifically for dynamic reactor environments, rather than relying solely on static screening data to predict industrial performance. It is concluded that cultivation in bioreactors for enzyme production must carefully consider agitation and aeration conditions, as these conditions modify the yeast's behavior, altering nutrient utilization and, consequently, the induction of enzymatic expression and cell growth.