Abstract Background During the last years B. megaterium was continuously developed as production host for the secretion of proteins into the growth medium. Here, recombinant production and export of B. megaterium ATCC14945 penicillin G amidase (PGA) which is used in the reverse synthesis of β-lactam antibiotics were systematically improved. Results For this purpose, the PGA leader peptide was replaced by the B. megaterium LipA counterpart. A production strain deficient in the extracellular protease NprM and in xylose utilization to prevent gene inducer deprivation was constructed and employed. A buffered mineral medium containing calcium ions and defined amino acid supplements for optimal PGA production was developed in microscale cultivations and scaled up to a 2 Liter bioreactor. Productivities of up to 40 mg PGA per L growth medium were reached. Conclusion The combination of genetic and medium optimization led to an overall 7-fold improvement of PGA production and export in B. megaterium. The exclusion of certain amino acids from the minimal medium led for the first time to higher volumetric PGA activities than obtained for complex medium cultivations.

Xylan degradation and production of beta-xylanase and beta-xylosidase activities were studied in cultures of Cellulomonas uda grown on purified xylan from birchwood. beta-Xylanase activity was found to be associated with the cells, although in various degrees. The formation of beta-xylanase activity was induced by xylotriose and repressed by xylose. beta-Xylosidase activity was cell bound. Both constitutive and inducible beta-xylosidase activities were suggested. beta-Xylanase and beta-xylosidase activities were inhibited competitively by xylose. beta-Xylanase activity had a pronounced optimum pH of 5.8, whereas the optimum pH of beta-xylosidase activity ranged from 5.4 to 6.1. The major products of xylan degradation by a crude preparation of beta-xylanase activity, in decreasing order of amount, were xylobiose, xylotriose, xylose, and small amounts of xylotetraose. This pattern suggests that beta-xylanase activity secreted by C. uda is of the endosplitting type. Supernatants of cultures grown on cellulose showed not only beta-glucanase but also beta-xylanase activity. The latter could be attributed to an endo-1,4-beta-glucanase activity which had a low beta-xylanase activity.