Production and Partial Purification of a Neutral Metalloprotease by Fungal Mixed Substrate Fermentation

Five strains of fungi belonging to Aspergillus sp. were evaluated by casein agar plate assay and a wheat bran-based solid-state fermentation for selecting a neutral protease-producing culture. Based on the results, A. oryzae NRRL 2217 was selected for further studies. Sixteen different agro-industrial residues were evaluated for their potential to serve as a substrate for neutral protease production by this fungal strain. Results showed that a combination of coconut oil cake and wheat bran in the mass ratio of 1:3 was the best substrate for enzyme production. Various process parameters influencing protease production including fermentation time, initial moisture content, and fermentation temperature were optimised. The medium was supplemented with different nutrients in the form of organic and inorganic nitrogen and carbon sources. Supplementation of chitin increased the enzyme production significantly. Ammonium nitrate as inorganic nitrogen supplement slightly enhanced enzyme production. No organic nitrogen supplement was effective enhancer of enzyme production. Fermentation was performed under optimised conditions (initial moisture content V/m = 50 %, temperature 30 °C, 48 h). Partial purification of the enzyme resulted in a 3-fold increase in the specific activity of the enzyme. The partially purified enzyme was characterised by various features that govern the enzyme activity such as assay temperature, assay pH and substrate concentration. The effect of various metal ions and known protease inhibitors on the enzyme activity was also studied. The enzyme was found to be stable in pH range 7.0–7.5, and at temperature of 50 °C for 35 min. By the activating effect of divalent cations (Mg2+, Ca2+, Fe2+) and inhibiting effect of certain chelating agents (EGTA, EDTA), the enzyme was found to be a metalloprotease

Jackfruit Seed – A Novel Substrate for the Production of Monascus Pigments through Solid-State Fermentation

Pigmenti iz gljive Monascus purpureus dobiveni su uzgojem kulture na čvrstoj podlozi od praha dobivenog mljevenjem sušenog sjemena biljke Artocarpus heterophyllus (Jackfruit). Boja dobivenih pigmenata bila je stabilna bez obzira na početnu pH-vrijednost supstrata zahvaljujući puferskom svojstvu praha. Najbolji supstrat za proizvodnju pigmenata bio je prah veličine čestica od 0,4 do 0,6 mm, bez dodanog izvora ugljika. Kad se prahu doda natrijev glutamat, sojina sačma, pepton ili hitinski prah, dobiju se pigmenti topljivi u vodi. Dodatak dušikovih spojeva pozitivno utječe na proizvodnju pigmenata topljivih u vodi.Solid-state fermentation was carried out using jackfruit seed powder as substrate for the production of pigments using a fungal culture of Monascus purpureus. Due to the buffering nature of jackfruit seed powder, colour of pigments produced was stable over a wide range of initial pH of the substrate. Jackfruit seed powder with a particle size between 0.4 and 0.6 mm without any additional carbon source was found to be the best for pigment production. Water-soluble pigments were produced when jackfruit seed powder was supplemented with monosodium glutamate, soybean meal, peptone or chitin powder. The addition of external nitrogenous compounds showed a positive impact on water-soluble pigment production

New Perspectives for Citric Acid Production and Application

U svijetu postoji velika potražnja za limunskom kiselinom zbog njezine male toksicnosti u usporedbi s ostalim regulatorima kiselosti koji se primijenjuju u farmaceutskoj i prehrambenoj industriji. Limunska se kiselina dodaje i detergentima, sredstvima za cišcenje, kozmetickim preparatima te higijenskim i ostalim proizvodima. Svjetska proizvodnja dosegla je 1,4 milijuna tona, a potražnja odnosno potrošnja limunske kiseline raste 3,5-4 % na godinu. Zbog rastuce potražnje na tržištu, opstali su samo veliki proizvodaci. Povecanje proizvodnje limunske kiseline osobito je važno pa je potrebno razmotriti sve nacine da bi se to postiglo. Danas još uvijek prevladava proizvodnja submerznim postupkom, a proizvodnja na cvrstoj podlozi otvara proizvodacima nove mogucnosti. Mnogi nusproizvodi u poljoprivredi mogu se upotrijebiti za proizvodnju limunske kiseline pa se time smanjenju troškovi proizvodnje. Uporaba jeftinijih supstrata za bioproces od ekonomske je i ekološke važnosti. Povecana proizvodnja limunske kiseline može se postici i primjenom sojeva poboljšanih mutagenezom i selekcijom.There is a great worldwide demand for citric acid consumption due to its low toxicity when compared with other acidulants used mainly in the pharmaceutical and food industries. Other applications of citric acid can be found in detergents and cleaning products, cosmetics and toiletries, and other. Global production has now reached 1.4 million tonnes and there is annual growth of 3.5–4.0 % in demand/consumption of citric acid. As a result of the adverse market conditions, only big producers have survived. Any increase in citric acid productivity would be of potential interest and hence there is an obvious need to consider all possible ways in which this might be achieved. The production by submerged fermentation is still dominating. However, solid-state processes can create new possibilities for producers. Many by-products and residues of the agro-industry can be used in the production of citric acid. A cost reduction in citric acid production can be achieved by using less expensive substrates. The use of agro-industrial residues as support in solid-state fermentation is economically important and minimizes environmental problems. Other perspectives for citric acid production sector are the improvement of citric acid producing strains, which have been carried out by mutagenesis and selection