Blog

In the present study

In the present study, local isolate of fungi, G. gibbosum and L. sajor -caju, were found to be highly ligninolytic and promising laccase producers. Within a short fermentation period of optimized SSF conditions (control conditions), they exhibited much higher level of laccase, LiP and MnP Fig (). The results are in conformity with similar findings made by other workers that some species of white rot fungi secrete only one or two LMEs (Elisashvili et al., 2008; Wong, 2009; Arora and Sharma, 2010). Such variations have also been reported in various Ganoderma spp. And strains exhibiting varying abilities to secrete LMEs; some species secrete all LMEs in good amount whereas others produced more laccase with either low level of MnP and LiP activities (Adaskaveg et al., 1990; D’Souza et al., 1999; De Souza Silva et al., 2005; Silva et al., 2005a; Ding et al., 2012; Zhou et al., 2013). Similar behaivour has also been reported in Lentinus spp. Lentinula edodes has been reported as laccase and MnP producers on solid media or during SSF on tree leaves (Hatvani and Mech, 2002; Silva et al., 2005b; Elisashvili et al., 2008) whereas CCB-42 strain of fungus was found to produce only MnP, with negligible amount of laccase and LiP on corn cob solid state cultures (Boer et al., 2004). Revankar et al. (2007) reported 10,050 IU/g laccase yield from indigenously isolated Ganoderma sp. In SSF on wheat bran supplemented with additional carbon and nitrogen source which is comparable to our indigenous isolate of Ganoderma sp. A higher yield of laccase (37,423 IU/g) has been reported in Ganoderma sp. rckk-02 under well optimized SSF of wheat bran (Sharma et al., 2015). Cultivation of both fungi under similar SSF conditions also revealed a wide difference between the two species in laccase production. The amount of laccase produced by Ganoderma sp was always more than Lentinus sp. Under control as well as surfactants treated conditions on both substrates (Fig). In the present study, laccase activity in both fungi increased many fold due to supplementation of substrate with all surfactants. The increase in enzyme activity on supplementation of surfactants may be due to increase in permeability of the cell membrane lipid bilayer facilitating rapid secretion of enzyme out of the cell. Moreover surfactant could also protect the enzyme structure and its activity from environmental factors forming micelles around the enzyme. Moreover in lignocellulosic structure solubility of compounds increases and thus providing larger surface area for utilization of fungus in presence of surfactants (Akpinar et al 2017). Non ionic surfactants such as Tween 20, 80, 100 are considered non toxic and they do not affect the fungal growth of S. ostrea (Usha et al., 2014). Similarly Ding et al., 2008 also found no negative effect of Tween 80 on P. chrysosporium growth and also found to have stimulatory effect on ligninolytic enzymes (Couto et al., 2004) and found to have stimulated LiP production in P. chrysosporium. In the present study further, for a particular fungus- substrate combination, the quantum increase in laccase activity by all the surfactants differed very narrowly except in the case of L. sajor – caju. saw dust combination where tween 20 proved much better than others. Usha et al. (2014) also found all surfactants (Tween 20, Tween 80 and Triton X-100) effective in enhancing laccase activity in Stereum ostrea grown on wheat bran. However, they reported maximum laccase activity with Tween 80 and Tween 20 and Triton X-100, whereas in the present study it was Tween 20 that induced a maximum of 39180 IU/g laccase in G. gibbosum. and 37780 IU/g in L. sajor – caju. corresponding to 3.8 and 10.6- fold increase over control condition. Lestan et al. (1994) reported an increase in yield with both Tween 20 and 80 supplementation. In the present study, Tween 80 could provide laccase activity comparable to Tween 20 in both fungi on saw dust but not on wheat bran where it is comparatively inferior. Asther et al. (1987), however, reported no enhancement in ligninase production with Tween 80 in Phanerochaete chrysosporium INA-12. Triton X-100 was found as the best surfactant for saw dust providing 29380 and 19877 IU/g laccase activity in G. gibbosum and L. sajor- caju, amounting to 2.9 and 3.9 fold increase over the control conditions. When grown on Triton X-100 treated saw dust, the laccase activity of these species was 30% less in comparision with their laccase activity on Tween 20 treated wheat bran. In comparision with Triton X-100, Tween 20 treated saw dust could also induce equivalent amount of laccase activity in L sajor -caju, and slightly less in G. gibbosum. LiP and MnP activities were very low, in comparision with laccase, in both fungi under control conditions (1.92 to 4.07 IU/g and 0.98 to 2.07 IU/g, respectively) and supplementation with surfactants did not show any appreciable quantitative change in their activity (Fig). As a result, ratio between laccase and LiP/MnP in surfactants treated conditions was much larger. In most of the cases, treatment of saw dust with surfactant improved MnP activity slightly but with a resultant decrease in LiP activity. On wheat bran, both MnP and LiP activities decreased slightly except in Tween 20 and Triton X treated conditions for G. gibbosum. Akpinar et al 2017 also reported that supplementation of surfactants at various concentrations to the medium stimulates the laccase activity. Maximum laccase activity was obtained at 20th day of incubation and at 17th day of control set. Maximum laccase activity obtained was 11.4 fold higher compared to the control. Usha et al. (2014) reported enhanced activity of MnP by surfactants in order of Tween 80, Tween 20, and Triton X-100, but without any enhancement in LiP activity. Urek and Pazarlioglu (2007) also reported 2-fold increase in MnP activity on Tween 80 supplementation. The result obtained in the study proved wheat bran as a better substrate than saw dust for laccase production in surfactant supplemented conditions and G. gibbosum always showed more laccase activity on this substrate (Fig 2). Similar observations have been made in other studies (Revankar et al., 2007; Elisashvili et al., 2009; Songulashvili et al., 2007). LiP and MnP activities on wheat bran and saw dust respectively were always found to be higher in both fungi in control as well as surfactant treated conditions.

x

Hi!
I'm Gloria!

Would you like to get a custom essay? How about receiving a customized one?

Check it out