Production of an alkaline xylanase from recombinant Kluyveromyces lactis (KY1) by submerged fermentation and its application in bio-bleaching

• Recombinant xylanase was produced using a Kluyveromyces lactis.
• Bioprocess optimization led four-fold increase in the production.
• Partially purified enzyme was effective for bio-bleaching.
• First report on the utility of a recombinant xylanase gene expressed in K. lactis for pulp bleaching.

The aim of this work was to study the production of recombinant xylanase using a Kluyveromyces lactis GG799 strain with a plasmid vector pKLAC1 carrying xylanase coding gene (XynA) isolated from Bacillus pumilus MTCC 5015. To obtain maximum xylanase expression, statistical approaches based on response surface methodology (RSM) was employed. Critical variables for recombinant xylanase production were identified by one-variable-at- a- time approach followed by response surface methodology (RSM), which led to an enhancement in extracellular xylanase production (200 IU/mL). Maximum xylanase production was obtained when 2% of casamino acid was used along with 5% of galactose (inducer) with an inoculum size of 2.75% (5 × 108 CFU/mL) when incubated for 48 h with a pre-inoculum age of 24 h (273 IU/mL). Thus, a four-fold increase in activity from 70 IU/mL to 273 IU/mL could be achieved. SDS-PAGE analysis showed that the relative molecular mass of glycosylated XynA was about 35.0 kDa. The partially purified enzyme was used for the bio-bleaching of paper carton, which showed its effective application in bleaching.