Bioprospecting microwave-alkaline hydrolysate cocktail of defatted soybean meal and jackfruit peel biomass as carrier additive of molasses-alginate-bead biofertilizer

Abstract

The extraction of soluble hydrolysate protein and sugar from a biomass cocktail of defatted soybean meal (DSM) and jackfruit peel (JP) was examined using microwave-alkaline hydrolysis by varying the NaOH concentrations (0.04-0.11 M) and residence times (2-11 min). Based on the central composite design, the optimized parameters were achieved at 0.084 M NaOH concentration (100 mL), for 8.7 min at 300 W microwave power level to obtain the highest protein (5.31 mg/mL) and sugar concentrations (8.07 mg/mL) with > 75% recovery. Both raw and detoxified hydrolysate (using activated carbon) were correspondingly biocompatible with Enterobacter hormaechei strain 40a (P > 0.05) resulting in maximal cell counts of > 10 log CFU/mL. The optimized hydrolysate was prepared as an additive in molasses-alginate bead encapsulation of strain 40a. Further evaluation on phosphate and potassium solubilization performance of the encapsulated strain 40a exhibited comparable results with those of free cell counterpart (P > 0.05). The DSM-JP hydrolysate cocktail holds potential as a carrier additive of encapsulated-cell bead biofertilizers in order to sustain bacterial cell quality and consequently improve crop growth and productivity.

Figure 1

Contour (a,c) and 3D (b,d) plots of the interaction between NaOH concentration and residence time in the MAH cocktail of DSM and JP on protein and sugar concentration of hydrolysate. The graphs were visualized in DOE software (v 11; Stat-Ease, Inc., MN, USA; www.statease.com).

Figure 2

Validation of the quadratic optimization model: contour plot of quadratic model desirability prediction (a); experimental runs of MAH of DSM-JP cocktail based on the predicted optimum parameters (b). Data presented are the means ± standard deviations from three independent experiments (Student’s t-test: *P < 0.05; **P < 0.01; ns P > 0.05). The graphs were visualized in DOE software (v 11; Stat-Ease, Inc., MN, USA; www.statease.com) and GraphPad PRISM software (v 8.02; GraphPad, Inc., MN, USA; www.graphpad.com).

Figure 3

Changes in the chemical structure of hydrolyzed DSM-JP: (a) FTIR spectra of raw, residue, and hydrolysate of DSM-JP; (b) amino acid and (c) sugar profiles of DSM-JP hydrolysate. Mean data of triplicate experiments were presented with error bars represent standard deviations. The graphs were visualized in GraphPad PRISM software (v 8.02; GraphPad, Inc., MN, USA; www.graphpad.com).

Figure 4

Biocompatibility assay of DSM-JP hydrolysate: (a) detoxification of hydrolysate using activated carbon (AC); (b) Growth of strain 40a in a raw and a detoxified hydrolysate media (c). nutrient utilization dynamics during 3-day growth of strain 40a. Data represent mean values ± standard deviations (n = 3). Different letters indicate statistically significant differences between factors (two-way ANOVA + Tukey multiple comparisons test at P < 0.05). The correlation coefficient was calculated by Pearson correlation. The graphs were visualized in GraphPad PRISM software (v 8.02; GraphPad, Inc., MN, USA; www.graphpad.com).

Figure 5

The visual image of SJMo-Alg bead 40a biofertilizer: (a) representative image of the freshly extruded bead; (b) SEM image of free cells of strain 40a; (c) SEM image of a single bead; (d) high magnification SEM image of encapsulated strain 40a on the surface of SJMo-Alg bead 40a.

Figure 6

Comparison of P and K solubilization activity of free cells and encapsulated cells of strain 40a (SJMo-Alg bead 40a). Data represent mean values ± standard deviations (n = 3). Different letters indicate statistically significant differences between factors (two-way ANOVA + Tukey multiple comparisons test at P < 0.05). The graphs were visualized in GraphPad PRISM software (v 8.02; GraphPad, Inc., MN, USA; www.graphpad.com).