Intensification of Freeze-Drying Rate ofBacillus subtilisMTCC 2396 Using Tungsten Halogen Radiation: Optimization of Moisture Content and α-Amylase Activity

Abstract

A novel freeze-drying protocol has been explored to render fast and cost-effective freeze drying of hyperamylase producing Bacillus subtilis MTCC2396 employing a tungsten halogen lamp radiator (THLR) as a heat source. Response surface methodology assessed the maximum reduction in moisture content (96.07%) and minimum reduction in a-amylase (EC 3.2.1.1) activity (1.02%) in 4 h drying time at 42.5 C radiation temperature. a-amylase activity (0.046 U) and final moisture content (3.93%) of the optimally freeze-dried bacterial strain appeared satisfactory. The freeze-drying time using THLR (4 h) is remarkably lower compared to that under a conventional conductive plate heater (CPH) (10 h) at otherwise identical conditions. The higher effective moisture diffusivity of 0.0052 to 0.0078 m 2 /s under THLR compared to 0.00084 to 0.0015 m 2 /s under CPH (corresponding to 20-50 C) advocated the superiority of the THLR heating protocol. The higher efficacy of THLR was also evidenced through lower activation energy (8.42 kJ/mol) of moisture diffusion compared to that (12.051 kJ/mol) of CPH. The optimally freeze-dried bacteria demonstrated the same growth rate in addition to exhibiting excellent retention of bioremedial (Hg 2þ removal) activity to that of the control.

Effect of Lyoprotective Agents on the Preservation of Survival of a Bacillus cereus Strain PBG in the Freeze-Drying Process

“…Strains of Bacillus cereus have been subjected to lyophilization processes to harness their potential as biocontrol agents against pathogens and for their effectiveness in mercury removal. These microorganisms have undergone lyophilization to stabilize the cells for future research, focusing on possible scaling-up applications and formulation development, as suggested in the studies by Bhattacharya et al (2016) and Bhattacharya et al (2014). In most cases, processes are evaluated post-lyophilization.…”

“…In most cases, processes are evaluated post-lyophilization. However, to ensure the long-term success of this process, it is essential to conduct assessments over time [92,93].…”

Development of microencapsulated dried Bacillus sp. 63‐11 with enhanced shelf stability and bioactivity for use as a food supplement

“…Freeze drying technique was modified from Bhattacharya et al . (2014). Cell pellet were centrifuged, harvested in 2 mL of 5% NaCl solution, and coated with MD or MS in two separate ratios of 1.8:3 and 2.4:3 respectively.…”

“…Total coliforms, yeast/mould count enumerated using Petri-film™ Rapid E. coli/coliform count plate (3 M, USA) and potato dextrose agar (Himedia, India). Water activity (a w ) was determined using a water activity metre (AQUALAB 4TE) at 25 AE 0.5 °C according to (AOAC and Latimer, 2019). The growth of osmophilic yeasts and xerophilic moulds are susceptible to water activity (a w ) <0.60.…”

Parametric sensitivity of pH and steady state multiplicity in a continuous stirred tank bioreactor (CSTBR) using a lactic acid bacterium (LAB),Pediococcus acidilactici

“…At each initial substrate concentration the microbial growth pattern was studied for 24 h. Samples were withdrawn at 2 h intervals during incubation. The biomass concentration of each sample was determined using a spectrophotometric method and glucose concentration was determined using the DNS method . Each sample was centrifuged at 10000 rpm and the supernatant was analyzed for lactic acid using HPLC.…”