Search

Fructooligosaccharides (FOS) have gained significant attention for their prebiotic properties. Given that sugarcane syrup (SS) is sucrose-rich but with other nutritional benefits, its direct transformation into FOS may add value to this product. Therefore, the aims of this study were to develop FOS conversion from SS and to define the kinetic behaviour of FOS synthesized in a 1-L specialized pH-stat bioreactor (SPSB). The SS was composed of sucrose (58.93%) with considerable antioxidant capacities and Ƴ-aminobutyric acid. The developed SPSB process consisted of three stages: evaporation of sugarcane juice into syrup (68–75 °Brix) (stage 1), optimization of the Viscozyme L and SS mixture at different reaction temperatures (47–55 °C) (stage 2), and upscaling of the optimized reaction system under defined conditions in a 1 L-SPSB system (stage 3). In the 1 L-SPSB system, the enzymatic reaction yielded 32.22% of FOS from SS after a 6 h reaction, which is comparable with a pure system containing an equivalent concentration of 10% of sucrose as initial substrate with 39.55% yield. This result demonstrated the efficient conversion of SS into FOS, supporting the utilization of sugarcane juice for its health benefits.

For centuries, Azadirachta indica or neem has been utilized as a primary source of medicine due to its antimicrobial, larvacidal, antimalarial and antifungal properties. Recently, its potential as an effective biopesticide has garnered attention, especially towards efficient and continuous production of its bioactive compounds. The present study investigated the effect of the plant growth regulators (PGRs) thiadiazuron (TDZ) and 2,4-dichlorophenoxyacetic acid (2,4-D) on the induction of colored callus formation and subsequent accumulation of azadirachtin (AZA) in A. indica. An efficient protocol was established for micropropagation and colored callus production of this species, followed by quantification of AZA (a mixture of azadirachtin A and B) and its safety assessment. For induction of the callus, leaf and petiole explants obtained from a young growing neem plant were excised and cultured on Murashige and Skoog (MS) medium supplemented with TDZ (0.2&ndash, 0.6 mg L-1) and 2,4-D (0.2&ndash, 0.6 mg L-1), either applied singly or in combination. Callus was successfully induced from both explant types at different rates, where media with 0.6 mg L-1 of TDZ resulted in the highest fresh weight (3.38 &plusmn, 0.08 g). In general, media with a single hormone (particularly TDZ) was more effective in producing a high mass of callus compared to combined PGRs. A culture duration of six weeks resulted in the production of green, brown and cream colored callus. The highest callus weight and accumulation of AZA was recorded in green callus [214.53 &plusmn, 33.63 mg g-1 dry weight (DW)] induced using TDZ. On the other hand, small amounts of AZA were detected in both brown and cream callus. Further experimentation indicated that the green callus with the highest AZA was found to be non-toxic (LC50 at 4606 &micro, g mL-1) to the zebrafish animal model. These results suggested that the addition of different PGRs during in vitro culture could prominently affect callus and secondary metabolite production and can further be manipulated as a sustainable method for the production of a natural and environmentally friendly pesticide.

This study investigates the effects of viscosity, friction, and sonication on the morphology and the production of lovastatin, (+)-geodin, and sulochrin by Aspergillus terreus ATCC 20542. Sodium alginate and gelatine were used to protect the fungal pellet from mechanical force by increasing the media viscosity. Sodium alginate stimulated the production of lovastatin by up to 329.0% and sulochrin by 128.7%, with inhibitory effect on (+)-geodin production at all concentrations used. However, the use of gelatine to increase viscosity significantly suppressed lovastatin, (+)-geodin, and sulochrin's production (maximum reduction at day 9 of 42.7, 60.8, and 68.3%, respectively), which indicated that the types of chemical play a major role in metabolite production. Higher viscosity increased both pellet biomass and size in all conditions. Friction significantly increased (+)-geodin's titre by 1527.5%, lovastatin by 511.1%, and sulochrin by 784.4% while reducing pellet biomass and size. Conversely, sonication produced disperse filamentous morphology with significantly lower metabolites. Sodium alginate-induced lovastatin and sulochrin production suggest that these metabolites are not affected by viscosity; rather, their production is affected by the specific action of certain chemicals. In contrast, low viscosity adversely affected (+)-geodin's production, while pellet disintegration can cause a significant production of (+)-geodin.

Carbon source is a key component of metabolites synthesis in microorganisms. This work examined the effects of selected carbon sources in the form of carbohydrates, on the growth of Aspergillus terreus ATCC 20542 and the production of lovastatin. Slowly metabolised carbohydrates, such as D-galactose (consumption rate, r=3.11), produced a high microbial biomass, XFINAL (9.44 g/L) compared to other carbohydrates, but with a low biomass yield coefficient (YLOV/X=1.68). In contrast, D-ribose (YLOV/X=) which showed moderate biomass growth (XFINAL=8.78 g/L) and consumption rate (r=5.44 g/day), produced the highest lovastatin amount (51.81 mg/L, day 6). These indicate little correlation between biomass growth and lovastatin production. Notably, culture consisting of pellets with short hairy surface feature is associated with enhanced lovastatin production. Our findings suggest that the production of lovastatin by Aspergillus terreus is highly influenced by the choice of carbohydrates that will shape the pellet morphology rather than the rate of carbohydrates metabolism.

Crude glycerol (CG) can be used as a substrate for microbial bioconversion. However, due to presence of many impurities, many microorganisms are unable to utilise this substrate efficiently. The present study is trying to improve CG using as the feedstock of Aspergillus terreus for the production of lovastatin, (+)-geodin, and sulochrin. The CG was pretreated chemically (solvents) and physically (activated carbon (AC) and water softener (WS)) to separate most of the impurities from the CG. For solvent pretreatments, petroleum ether (PE) produced the largest increase of lovastatin (92.8%) when compared to positive control and pure glycerol (PG) and up to 820% when compared to negative control (CG). In contrast, diethyl ether (DE) produced the largest increase in (+)-geodin at 80.81% (versus CG) and 176.23% (versus PG). The largest increase in toluene (Tol) was observed in sulochrin production, at 67.22% (versus CG) and 183.85% (versus PG). For physical pretreatments, the pattern of metabolite production in AC (lovastatin: 20.65 mg/L, (+)-geodin: 7.42 mg/L, sulochrin: 11.74 mg/L) resembled PG (lovastatin: 21.8 mg/L, (+)-geodin: 8.60 mg/L, sulochrin: 8.18 mg/L), while WS (lovastatin: 11.25 mg/L, (+)-geodin: 15.38 mg/L, sulochrin: 16.85 mg/L) resembled CG (lovastatin: 7.1 mg/L, (+)-geodin: 17.10 mg/L, sulochrin: 14.78 mg/L) at day 6 of fermentation. These results indicate that solvent pretreatments on CG are excellent for metabolites production in A. terreus, depending on the solvents used. In contrast, physical pretreatments are only feasible for (+)-geodin and sulochrin production. Therefore, different strategies can be employed to manipulate the A. terreus bioconversion using improved CG by using a few simple pretreatment strategies.

Lovastatin is widely prescribed to reduce elevated levels of cholesterol and prevent heart-related diseases. Cultivation of Aspergillus terreus (ATCC 20542) with carbohydrates or low-value feedstocks such as glycerol produces lovastatin as a secondary metabolite and (+)-geodin as a by-product. An A. terreus mutant strain was developed (gedCΔ) with a disrupted (+)-geodin biosynthesis pathway. The gedCΔ mutant was created by inserting the antibiotic marker hygromycin B (hyg) within the gedC gene that encodes emodin anthrone polyketide synthase (PKS), a primary gene responsible for initiating (+)-geodin biosynthesis. The effects of emodin anthrone PKS gene disruption on (+)-geodin and lovastatin biosynthesis and the production of the precursors acetyl-CoA and malonyl-CoA were investigated with cultures based on glycerol alone and in combination with lactose. The gedCΔ strain showed improved lovastatin production, particularly when cultivated on the glycerol-lactose mixture, increasing lovastatin production by 80% (113 mg/L) while simultaneously inhibiting (+)-geodin biosynthesis compared to the wild-type strain. This study thus shows that suppression of the (+)-geodin pathway increases lovastatin yield and demonstrates a practical approach of manipulating carbon flux by modulating enzyme activity.

In this study, a selected γ-aminobutyric acid (GABA)-rich Malaysian strain Aspergillus oryzae NSK was collected from soy sauce koji. The strain was used to explore the effect of using renewable native sugar syrup, sugarcane, nipa, and molasses as fermentable substrates for developing a novel functional GABA soy sauce. We evaluated the strain using the chosen native sugars for 7 days using shake flask fermentation at 30 °C. The results showed optimum GABA concentration was achieved using cane molasses as the fermentable substrate (354.08 mg/L), followed by sugarcane syrup (320.7 mg/L) and nipa syrup (232.07 mg/L). Cane molasses was subsequently utilized as a substrate to determine the most suitable concentration for A. oryzae NSK to enhance GABA production and was determined as 50% g/L of glucose standard cane molasses. Our findings indicate that cane molasses can be used as a GABA-rich ingredient to develop a new starter culture for A. oryzae NSK soy sauce production.