BackgroundLignin peroxidase (LiP) is the primary enzyme responsible for lignin degradation. In our previous work, in order to shorten the pretreatment time and increase the lignin degradation, we have pretreated the corn stalk (CS) using a combination of Aspergillus oryzae CGMCC 5992 solid-state fermentation and H2O2 treatment.ResultsIn the present study, one-factor-at-a-time design and response surface design were applied to optimize the nutritional constituents for LiP production in liquid-state fermentation by A. oryzae CGMCC 5992 and the conditions for CS degradation by A. oryzae CGMCC 5992. The optimal medium included CS of 30 g/L, glucose of 4.6 g/L, sodium nitrate of 1.2 g/L, corn steep liquor of 1 g/L, yeast extract of 1.2 g/L, and vitamin B1 of 0.15 g/L. Under these optimal conditions, the LiP production reached its maximum of 652.34 U/L. The optimal condition for CS degradation included CS of 20 g, A. oryzae CGMCC 5992 broth of 50 mL, 1.5 % H2O2 solution of 80 mL, H2O2 flow rate of 0.4 mL/min, water volume of 240 mL (water/material ratio of 12:1), hydrolysis temperature of 39 °C, and hydrolysis time of 8 h. Before hydrolysis, CS and water were pretreated at 113 °C for 11 min. Under these optimal conditions, the sugar yield reached its maximum of 46.28 %.ConclusionsOur newly developed method had great advantages in pretreatment of CS due to its quickness, convenience, safety, no special equipment and high sugar yield.Graphical abstractThe schematic diagram of corn straw hydrolysisElectronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0362-4) contains supplementary material, which is available to authorized users.

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ε-Polylysine (ε-PL) is a highly safe natural food preservative with a broad antimicrobial spectrum, excellent corrosion resistances, and great commercial potentials. In the present work, we evaluated theε-PL adsorption performances of HZB-3B and D155 resins and optimized the adsorption and desorption conditions by single-factor test, response surface method, and orthogonal design. The complexes of resin andε-PL were characterized by SEM and FITR. The results indicated that D155 resin had the bestε-PL adsorption performance and was selected for the separation and purification ofε-PL. The conditions for the static adsorption ofε-PL on D155 resin were optimized as follows:ε-PL solution 40 g/L, pH 8.5, resins 15 g/L, and absorption time 14 h. The adsorption efficiency ofε-PL under the optimal conditions was 96.84%. Theε-PL adsorbed on the D155 resin was easily desorbed with 0.4 mol/L HCl at 30°C in 10 h. The highest desorption efficiency was 97.57% and the overall recovery ofε-PL was 94.49% under the optimal conditions. The excellentε-PL adsorption and desorption properties of D155 resin including high selectivity and adsorption capacity, easy desorption, and high stability make it a good candidate for the isolation ofε-PL from fermentation broths.

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