Strategies to Improve Enzymes via Solid-State Fermentation

Abstract

Solid-state fermentation (SSF) is the fermentation process which occurs on a solid surface in the absence of “free” water, where the moisture is absorbed to the solid matrix. SSF is gaining an advantageous edge over other fermentation techniques due to its less complexity and more proximity to the normal environment of many microorganisms. On the other hand, a difficulty arises while estimating the biomass concentration in solid-state fermentation. Various factors like direct product application, the increased concentration of the product, less cost of production, and reduced energy requirement are responsible in making SSF as one of the potent technologies for various enzyme productions as seen in case of cellulase, tannase, and lipase. Improvisation of cellulase production in solid-state fermentation can be achieved to a greater extent by making use of varying degrees of substrates which are lignocellulosic in nature, the implicated microorganisms, culture, and process parameters like moisture content and water activity, nutrients diffusion, size of substrate particle, pH, temperature, surfactants, and bioreactor designs. Submerged fermentation whereas holds a different place in terms of various types of fermentations as it has only one major problem related to the oxygen transfer to microorganisms which in turn depends on the configuration, size, and the agitation/aeration system used in the reactor. In order to characterize oxygen transfer, a parameter is known as K La (oxygen transfer coefficient) whose value gives the estimation that how much of the oxygen is transferred by the equipment independent of the reactor volume and hence, for scale-up studies, it becomes an important parameter. In case of antioxidants production using SSF, it was observed that pomace tends to increase the antioxidant activity convergent with an increase in activity of β-glucosidase. Different studies tend to show that P. floridensis as an important organism used during the production of lingo cellulolytic enzyme and consecutive advancement in in vitro digestibility of wheat straw has been carried out to a larger extent.