## 4 Conventional Formulations vs. Advanced Formulations--A Necessity for Advanced Carrier Systems  
Conventional biofertilizers are used in plant applications as powder, liquid, or granulated forms [2]. Inoculants are generally commercialized in solid and liquid forms--while liquid forms are applied to the seeds, granular inoculants are applied to the soil [64]. There are limitations in the use of conventionally immobilized biological agents for agricultural purposes. Unfortunately, conventional formulations encounter several problems like the low viability of microorganisms during storage and field applications, mainly due to the temperature changes and negative impact of other environmental factors [65]. For example, live _Trichoderma_ spores must be stored under refrigeration and applied at temperatures below 28 \({}^{\circ}\)C. The field applications must be performed under specific conditions as high relative humidity, and one of the biggest problems is ultraviolet light, which is harmful to the species [38; 66]. In the past, seed coated peat-based inoculants were the most popular commercially available inoculants on the market because of the positive effect of peat on storage and application. A significant problem of peat-based products is their negative environmental impact. Even though peat is a good carrier for microorganisms, interests in developing new formulations are of main interest [67]. Liquid inoculants are more approachable, due to the simpler production process, with relatively easy application. Again, there are also  
Figure 2: An example of a microdroplet generator used to prepare microparticles, Encapsulator Büchi-B390, BüCHI Labortechnik AG, Switzerland. problems with liquid inoculants because microorganisms' survival is inferior, due to the lack of carrier protection [68]. Alternative formulations are always developing, mainly to achieve the advantage of long shelf life and easy transportation while reducing the overall cost of preparation. Encapsulation of microorganisms into biopolymer-based particles mainly tries to enhance efficiency, achieve effective storage and transportation. Encapsulated microorganisms have enhanced survival and controlled release with prolonged effect with the higher performance during storage and applications [2]. Increasing the bioavailability of biological control agents in the field is also possible with the use of encapsulation into biopolymeric microparticles. Especially, since biopolymeric microparticles are high in water content, instantly resolving the problem with the necessity of high relative humidity. Advanced carrier systems would be made via the simple and economic process, using biodegradable and safe material for delivering more than one active ingredient (chemical/biological), with tunable release properties and greater shelf-life compared to the conventional formulations. Biopolymeric microparticles can engulf microorganisms and protect them with their predefined and fixed microenvironment for the cells' survival. Thus, the cell metabolic activity can be maintained over an extended period. Except for serving as an energy source for the microorganisms, due to its deterioration, biopolymeric microcapsules allow the controlled release of microorganisms [65; 69]. It must be noted that when choosing a relevant biopolymer, its characteristics need to be considered to achieve successful biological control. Important physicochemical parameters to consider when using a biopolymer are molecular weight and distribution, degree of substitution, opposite ions, gelation mechanism, pH, viscoelasticity, primary, secondary, and tertiary structures. Of course, economic factors as cost should always be considered. Safety, quality, and source of biopolymers are also important factors to be considered, as well as degradability and approval from relevant agencies (European Union Commission Regulation, Food and Drug Administration, etc.) [38].